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Atomic Structure   Student Copy
 

Atomic Structure Student Copy

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    Atomic Structure   Student Copy Atomic Structure Student Copy Presentation Transcript

    • ATOMIC STRUCTURE 1. Relate the number of protons, neutrons and electrons in an atom (including isotopes) or a monatomic ion, to the atomic number, mass number and charge. 2. State the electron arrangement of atoms and/or ions of the first 20 elements in the Periodic Table. 3. Relate the charge on monatomic ions to the position of the element on the Periodic Table. 4. State the electron arrangement of atoms and/or ions of the first 20 elements in the Periodic Table. 5. Relate the charge on monatomic ions to the position of the element in the Periodic Table 6. Draw Lewis diagrams of : • atoms selected from the first 20 elements • molecules including those with single bonds, e.g. H2O, CH4, H2, Cl2 & PCl3 and those with multiple bonds Monday, 3 May 2010
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    • Monday, 3 May 2010
    • Term Definition GLOSSARY 1 In back of book: match term with defn -> ans’s only A. atom 1. the absence of electrical charge. B. element 2. a negatively charged particle that exists outside the nucleus 3. refers to electrons that occupy the outside shell or highest C. proton energy level around a nucleus D. electron 4. a substance that contains only one type of atom 5. the number of particles (protons & neutrons) in the nucleus of E. neutron the atom F. neutral 6. a positively charged particle in the nucleus. G. atomic number 7. a row of the periodic table 8. the smallest particle that can not be made smaller by simple H. mass number chemical means 9. an atom that has the same atomic number as another atom I. group but a different mass number J. period 10. a particle inside the nucleus that has no charge K. valence 11. the number of protons in the nucleus of an atom 12. a rule that states that most atoms will have a tendency to gain L. relative a full outer shell of 8 valence electrons M. isotope 13. a vertical column of the periodic table N. octet rule 14. compared to Monday, 3 May 2010
    • Term Definition GLOSSARY 1 the smallest particle that can not be made smaller by simple atom chemical means element a substance that contains only one type of atom proton a positively charged particle in the nucleus. electron a negatively charged particle that exists outside the nucleus neutron a particle inside the nucleus that has no charge neutral the absence of electrical charge. atomic number the number of protons in the nucleus of an atom the number of particles (protons & neutrons) in the nucleus of mass number the atom group a vertical column of the periodic table period a row of the periodic table refers to electrons that occupy the outside shell or highest valence energy level around a nucleus relative compared to an atom that has the same atomic number as another atom but isotope a different mass number a rule that states that most atoms will have a tendency to gain octet rule a full outer shell of 8 valence electrons Monday, 3 May 2010
    • Term Definition GLOSSARY 2 In back of book: match term with defn -> ans’s only A. a model of a molecule that shows valence electrons as bonding and 1. duet rule non-bonding pairs 2. valence B. the flow of charge 3. molecule C. a 3D, regular arrangement of particles (ions). 4. crystal D. a non-bonding pair of electrons E. a bond that comprises three pairs of electrons that are shared 5. lattice between two nuclei 6. Lewis F. the rule that is obeyed by hydrogen, stating that a hydrogen atom will structure have a tendency to gain a full outer shell of two electrons. 7. lone pair G. a solid substance that has sharp edges and flat faces 8. single bond H. refers to electrons that occupy the highest energy level of an atom 9. double bond I. a small group of atoms that are covalently bonded to each other J. a bond that comprises two pairs of electrons that are shared 10. triple bond between two nuclei 11. anion K. a positively charged ion 12. cation L. a negatively charged ion 13. reactivity M. a measure of the ability of a substance to dissolve in a solvent N. a bond that comprises one pair of electrons that are shared 14. solubility between two nuclei O. a measure of the ability of a substance to participate in a chemical 15. electric current reaction Monday, 3 May 2010
    • Term Definition GLOSSARY 2 the rule that is obeyed by hydrogen stating that a hydrogen atom will duet rule have a tendency to gain a full outer shell of two electrons. valence refers to electrons that occupy the highest energy level of an atom molecule a small group of atoms that are covalently bonded to each other crystal a solid substance that has sharp edges and flat faces lattice a 3D, regular arrangement of particles (ions). Lewis a model of a molecule that shows valence electrons as bonding and structure non-bonding pairs lone pair a non-bonding pair of electrons a bond that comprises one pair of electrons that are shared single bond between two nuclei a bond that comprises two pairs of electrons that are shared double bond between two nuclei a bond that comprises three pairs of electrons that are shared triple bond between two nuclei anion a negatively charged ion cation a positively charged ion a measure of the ability of a substance to participate in a chemical reactivity reaction solubility a measure of the ability of a substance to dissolve in a solvent electric current the flow of charge Monday, 3 May 2010
    • REVISION Monday, 3 May 2010
    • BASICS Monday, 3 May 2010
    • Elements THE BASICS Complete: Elements are like the letters of the alphabet. There are 26 letters and these can be joined together in different ways to make up to 750 000 different words. Letters cannot be split into anything simpler. • Elements are substances that contain particles called . • An element consists of only one type of atom only. • Atoms cannot be easily into anything . • There are 90 different elements and these can be . to make all the other in the world Atoms Part of Where Electrical atom found Charge Proton + + Neutron Proton Electron Word list: substances, atoms, simpler, split, joined, proton, electron, empty space, negative, positive, neutral, neutron, in the “History of the atom” nucleus, outside the nucleus. Monday, 3 May 2010
    • Element names H Na He Mg Li Al Be Si B P C S N Cl O Ar F K Ne Ca An easy way to remember the first 20 elements Flashcards (in exercises) Harry He Likes Beer By Cupfuls Not Over Flowing Never Natter Magic Although Science Possesses Some Clues Arthur Kicks Cats “Element Bingo” (in starters) Monday, 3 May 2010
    • ELECTRON ARRANGEMENTS Monday, 3 May 2010
    • THE PERIODIC TABLE Hydrogen - not a metal but here because of its electron arrangement 1 2 3 4 5 6 7 8 Non-metals Less reactive More reactive metals Inert gases metals Monday, 3 May 2010
    • ORGANISATION OF THE PERIODIC TABLE Atomic number Atomic numbers are the smaller of the two numbers associated with each element. Atomic numbers increase by one from left to right of the table Rows The atoms get larger in size from left to right across a row as their mass increases Columns The atoms get larger in size and increase in mass from top to bottom of a column. Elements in a column have similar properties. Columns are often called groups. Groups start at 1 (at the left) and finish with group 8 (at the right of the table) Monday, 3 May 2010
    • Monday, 3 May 2010
    • MASS NUMBERS & ATOMIC NUMBERS An element in the periodic table is described like this: The mass number is 19. 19 The number of protons plus neutrons =19 9 F Fluorine The atomic number is 9. There are 9 protons in the nucleus and 9 electrons around it In this example: The 19 particles in the nucleus are protons or neutrons I’m lost! 9 of these particles are protons therefore there are 10 neutrons in the nucleus Summary For an atom: • The atomic number gives the number of protons • The atomic number is also gives the number of electrons • The mass number is the number of protons plus neutrons • neutron number = mass number - atomic number Monday, 3 May 2010
    • An exercise done as a class: 4 He This shows how Helium appears in the periodic table 2 Helium This means: The atomic number is ___. so there are: 2 protons in the nucleus and 2 electrons surrounding it The mass number is ____. so the number of protons plus neutrons =4 Therefore the number of neutrons must be ___ ( = __ - __) number of Symbol of element number of protons number of neutrons electrons 11 B 5 16 O 8 28 Si 14 35 Cl 20 31 P 15 Monday, 3 May 2010
    • Individual Exercise TRY THIS! number of Symbol of element number of protons number of neutrons electrons 9 Be 4 21 Ne 10 27 Al 13 39 K 20 15P 16 42 Ca 20 12 C 6 7 Li 3 23 Na 11 24 Mg 12 14 N 7 16S 16 Monday, 3 May 2010
    • ELECTRON ARRANGEMENTS Electrons in the electron cloud are not arranged randomly around the nucleus. • Those close to the nucleus have low energy • Those far away from the nucleus have high energy Electrons are arranged in energy levels For the 1st 20 elements there are 4 energy levels: Level 1 can hold a maximum of 2 electrons Level 2 “ “ “ “ “ 8 electrons Level 3 “ “ “ “ “ 8 electrons Level 4 “ “ “ “ “ 2 electrons Example 1 20 protons in the nucleus 20 (the atomic number) Ca => 20 electrons around the 40 nucleus 2.8.8.2 Electron arrangement: “ 2 in the 1st shell, 8 in the 2nd shell, ....... Monday, 3 May 2010
    • CONFIGURE THIS! Use your knowledge of electron arrangement to complete the table below. The electron 1 arrangements are shown below H 1 the element names Hydrogen 1 4 2 He Helium 2 7 9 11 12 14 16 19 20 3 Li 4 Be 5 B 6 C 7 N 8 O 9 F 10 Ne Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon 2.1 2.2 2.3 2.4 23 24 27 28 31 32 37 40 11 Na 12 Mg 13 Al 14 Si P S Cl Ar Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon 2.8.1 39 40 K Ca Potassium Calcium Monday, 3 May 2010
    • SHELL DIAGRAMS Electrons fill up an atoms shell in order, first they fill up the inner shell (first electron shell) then the next shell and so on An exercise done as a class: Process: 40 x 1. Use your periodic table to find the atomic Ca x x x x x x number. x x Calcium x x x 2. The atomic number will tell you how x x x many electrons there are x x x x x Ca 3. Fill the electrons according to the rule: Level 1 can hold a maximum of 2 electrons Example 2 - Silicon Level 2 “ “ “ “ “ 8 electrons Level 3 “ “ “ “ “ 8 electrons 14 28 Level 4 “ “ “ “ “ 2 electrons Si 28 4. Start filling the levels from level 1. 2.8.4 5. When level 1 is full start filling level 2. When Si level 2 is full start filling level 3 and so on. 6. Stop filling the levels when you have used all the electrons that the atom has. Monday, 3 May 2010
    • Individual Exercise A DIFFERENT WAY OF SHOWING IT! Key: p = proton n = neutron Example: Fluorine, 9 19F has 9p, 10n, 9e e = electron e e For each of the following atoms draw the electron shell diagram. Show the nucleus as a solid circle. n p e e e n p p n p n n p A second example n p p p n n n e n p 1. 13 27Al x 2. 11 23Na x e x x x x x x x e x x x e x 3. 14 28Si 4. 15 31P 5. 16 32S Homework (in science books): (i) Be (ii) F (iii) Ne (iv) Ar Monday, 3 May 2010
    • Monday, 3 May 2010
    • Monday, 3 May 2010
    • Monday, 3 May 2010
    • ATOMS TO IONS Monday, 3 May 2010
    • ATOMS TO IONS An ion is an atom that has lost or gained electrons “Ions are more stable than atoms. IONS HAVE AN OUTER SHELL THAT IS FULL... Using this knowledge it is possible to work out the arrangement of electrons in ions.” Sodium atom --> Sodium ion 1 electron E x x x x x lost x X x x x x x x x x A x x x x x x x 1+ charge M Na Na+ P Chlorine atom --> Chloride ion 1 electron L x x x x x x x x x gained x x x x x E x x x x x x x x x x x S x x x x x x x x x x Cl Cl- 1- charge Monday, 3 May 2010
    • IRONING OUT THE IONS “Metal atoms lose electrons. Non-metal atoms gain electrons. No more than 3 electrons can be lost or gained” Copy & complete the following table showing the electron arrangements of the atoms and their ions: Metal atom Metal ion Non-metal atom Non-metal ion C: 2, 4 no ion formed Cl: 2, 8, 7 Cl-: 2, 8, 8 Mg: 2, 8, 2 Mg2+: 2, 8 N: 2, 5 N3-: 2, 8 Li: 2, 1 Li+: 2 Ar: 2, 8, 8 No ion formed Be O Ca S Al F Na P Draw small Beryllium Sulphide Aluminium shell diagrams for the following ions Monday, 3 May 2010
    • FORMULAE FOR SIMPLE IONS Background A chemical formula shows how atoms or ions are joined to make compounds. (A compound consists of two or more different atoms that are joined chemically). An ionic compound is formed when positive and negative ions are attracted to each other. Some ions comprise groups of atoms that have gained or lost electrons. These groups are the “-ides” or “-ates”. A table of common ions is shown below: +1 +2 +3 _,, -1 H* Mg2* Al3+ c1- gz- hydrogen magnesium aluminium chloride oxide Li* Ca2* Fe3* oH- COr'- lithium calcium iron(III) hydroxide carbonate Na+ Fe2* No,* Soo'- sodium iron(II) nitrate sulfate K+ Cu2* HCO3- PO43- potasslum copper(II) hydrogen carbonate Phosphate Zn2* zinc Pb2+ lead Monday, 3 May 2010
    • GETTING TO KNOW THE “-IDES” AND “-ATES” “-ates” end in O4 and O3 An exercise done as a class: the rest are “-ides” + ion - ion Formula + ion - ron Formula Znzr N3- ZneNz Ca2* NOs- Ca(NOs)z Pb2* Br PbBrz Fe3* SO+2- Fe2(S04)3 I Ag* s2- Li* COs2- LizCOs ) Fe3* cl- 6 Ag* PO+3- 3 Na* 02- 7 NH+* SO+2- K+ t- KI 8 Pbz* COs2- Cu2* SO+2- CuSOa 9 Al3* oH- 4 Mgz+ COs2- 10 Cu2* s2- 5 Zn2* 02- 11 (+ HCOg- On the table (above): 1. Circle the “-ates” using a red pen 2. Circle the “-ides” using a blue pen 3. and name them Exercises: “-ide or -ate” Monday, 3 May 2010
    • ION FORMATION AND THE PERIODIC TABLE 1 2 Groups of the periodic table 3 4 5 6 7 8 1+ 2+ Charge on ions formed by atoms in each group 3+ 3- 2- 1- Do not form ions Monday, 3 May 2010
    • INTRODUCTION Monday, 3 May 2010
    • HISTORY of the atom See “Nigel’s” ppt on the shared drive Monday, 3 May 2010
    • NOTES Monday, 3 May 2010
    • MATTER Nature & State Monday, 3 May 2010
    • PROPERTIES OF SOLIDS, LIQUIDS AND GASES BOB: Unscramble Appearance & Particles Energy Compressibility Melting & behaviour in a arrangement boiling container points A D. Particles are G. The very high J. high M. Moderate disordered energy of the and widely particles SOLID spaced causes random & rapid E. Particles H. The low K. very little N. High closely energy of the spaced & particles arranged in causes them LIQUID B a lattice. to vibrate This explains about fixed the positions crystalline appearance F. Particles are I. The moderate L. virtually O. Low disordered energy of the none and closely particles GAS C spaced causes them to move randomly Answers: SOLID __ __ __ __ __ LIQUID __ __ __ __ __ GAS __ __ __ __ __ Monday, 3 May 2010
    • http:// PROPERTIES OF SOLIDS, LIQUIDS AND GASES www.harcourtschool.com/ activity/states_of_matter/ Appearance & Particles Energy Compressibility Melting & behaviour in a arrangement boiling container points Particles are The low energy virtually none High closely of the particles spaced and causes them to arranged in a vibrate about SOLID fixed positions lattice. This explains the crystalline appearance Particles are The moderate very little Moderate disordered energy of the LIQUID and closely particles causes spaced them to move randomly Particles are The very high high Low disordered energy of the GAS and widely particles causes spaced random & rapid movement Monday, 3 May 2010
    • CHANGES OF STATE Monday, 3 May 2010
    • ATOMS, ELEMENTS, COMPOUNDS & MIXTURES P U R E Element Element Compound N O T P U R E Mixture Mixture of elements of element with compound Monday, 3 May 2010
    • Interactive Complete the mind map All substances X .............. Not pure ................... Elements ................... Element ................ with Different elements compound ................. Questions 1. Explain the difference between Co and CO __________________________________________________________________ __________________________________________________________________ 2. Explain the difference between O2 and 2O __________________________________________________________________ __________________________________________________________________ Monday, 3 May 2010
    • Copy ATOMS, ELEMENTS, COMPOUNDS & MIXTURES • An atom is a particle that cannot be made smaller by simple chemical methods. • An element is a substance that contains only one type of atom. • A compound is a substance that contains two or more types of atom chemically joined together in a constant ration by mass. • A mixture contains two or more different types of particle. • A solution is a special mixture where the solid particles are spread evenly throughout a liquid medium All substances Pure Not pure Mixture Elements Compounds Element Different with Different elements compound compounds Ex 3A: 1 to 4 - Answers only Monday, 3 May 2010
    • SEPARATING MIXTURES Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: 1. Salt added to water will form a ______________. 2. Salt is an example of an _________ solid 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list lattice sodium ionic flat chloride sharp solution crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. 2. Salt is an example of an _________ solid 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list lattice sodium ionic flat chloride sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list lattice sodium flat chloride sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list lattice flat chloride sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list lattice flat sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . lattice 4. Theses ions arrange themselves into a _____________. 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list flat sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. lattice 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list flat sharp crystalline Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. lattice crystalline 5. Solids with __________ structures have a _____________ appearance. This means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list flat sharp Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. lattice crystalline 5. Solids with __________ structures have a _____________ appearance. This sharp means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list flat Monday, 3 May 2010
    • SOLUTIONS PRE - TEST (out of 8) Use the diagram, word list and prior knowledge to complete the cloze exercise: solution 1. Salt added to water will form a ______________. ionic 2. Salt is an example of an _________ solid sodium chloride 3. The ions present in salt are ___________ and _____________ . 4. Theses ions arrange themselves into a _____________. lattice crystalline 5. Solids with __________ structures have a _____________ appearance. This sharp flat means the visible particles have __________ edges and __________ faces. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Word list Monday, 3 May 2010
    • SEPARATING MIXTURES SOLUTIONS VIDEO Monday, 3 May 2010
    • Solutions SEPARATING MIXTURES http://phet.colorado.edu/new/simulations/sims.php?sim=Salts_and_Solubility An animation showing how substances dissolve: Solvent Solute Solution Reading with exercises -> Monday, 3 May 2010
    • SEPARATING MIXTURES • Separation techniques based on the differences in the physical properties of the substances making up the mixture. Separation Why it can be separated using this Type of mixture technique technique Decanting The particles in the mixture are different Suspension (Liquid & sizes. Small liquid and solid particles insoluble solid) pass through whilst larger solid particles Filtration do not The solvent has a lower boiling point and evaporates away. In the case of two Solution (containing a Evaporation liquids that are mixed, the liquid with the solvent & a solute or lower boiling point will evaporate away two liquids that are mixed) Based on evaporation but allows the Distillation solvent or high boiling point liquid to be kept Different solvents have different Solutions that contain solubility in the solvent used so they Chromatography travel at different speeds alont the many solutes chromatography paper Monday, 3 May 2010
    • ISOTOPES & ATOMIC MASS Monday, 3 May 2010
    • ATOMIC THEORY History 1803 - Dalton’s model: “Atoms are indestructible spheres” 1911 - Rutherford: An atom is mainly empty space. It has a central dense, positively charged nucleus. The nucleus is tiny compared to the overall size of the atom. 1932 - Chadwick shows that neutrons exist Atoms Electron + Neutron + Proton Part of Where Relative Electrical atom found mass Charge Proton nucleus 1 positive Neutron nucleus 1 neutral outside Electron 0.0005 negative nucleus p31 & 32 - ESA -> Ex. 4A: Q.1 to 4 - answers only Monday, 3 May 2010
    • ISOTOPES 16 17 18 O O O 8 8 8 Monday, 3 May 2010
    • ISOTOPES Atoms with the same atomic number but different mass numbers. Example Below are the symbols of the common isotopes of Oxygen. Notice that the mass numbers are different 16 17 18 O O O 8 8 8 Each isotope has 8 protons 8 neutrons 9 neutrons 10 neutrons Each different isotope has different numbers of neutrons Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. The atomic mass of an element is the weighted average of the mass numbers of all the isotopes in that element. Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. The atomic mass of an element is the weighted average of the mass numbers of all the isotopes in that element. Example A naturally occurring sample of Copper has 3 atoms of 63 Cu to each one atom of 65 Cu: 63 Cu 63 Cu 63 Cu 65 Cu Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. The atomic mass of an element is the weighted average of the mass numbers of all the isotopes in that element. Example A naturally occurring sample of Copper has 3 atoms of 63 Cu to each one atom of 65 Cu: Atomic mass = 63 + 63 + 63 + 65 63 Cu 63 Cu 63 Cu 65 Cu 4 = 63.5 (or “3 x 63 + 65”) Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. The atomic mass of an element is the weighted average of the mass numbers of all the isotopes in that element. Example A naturally occurring sample of Copper has 3 atoms of 63 Cu to each one atom of 65 Cu: Atomic mass = 63 + 63 + 63 + 65 63 Cu 63 Cu 63 Cu 65 Cu 4 = 63.5 (or “3 x 63 + 65”) Chlorine is another element which consists of different isotopes. It has an atomic mass of 35.5 Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ATOMIC MASS An isotope has a mass number. An element that consists of different isotopes will have an atomic mass. The atomic mass of an element is the weighted average of the mass numbers of all the isotopes in that element. Example A naturally occurring sample of Copper has 3 atoms of 63 Cu to each one atom of 65 Cu: Atomic mass = 63 + 63 + 63 + 65 63 Cu 63 Cu 63 Cu 65 Cu 4 = 63.5 (or “3 x 63 + 65”) Chlorine is another element which consists of different isotopes. It has an atomic mass of 35.5 Most elements consist mainly of one isotope and therefore their atomic mass is close to a whole number. Ex 4B Q.1 to 3 - answers only Monday, 3 May 2010
    • ESA p41 Boron is unshaded because it does not covalently bond with itself?? LEWIS STRUCTURES I Monday, 3 May 2010
    • ELECTRON CONFIGURATION • Electrons around the nucleus of the atom have different levels of energy: • High energy electrons move in regions which are further away from the nucleus than low energy electrons. Level 1 can hold a maximum of 2 electrons Level 2 “ “ “ “ “ 8 electrons Level 3 “ “ “ “ “ 8 electrons Level 4 “ “ “ “ “ 2 electrons • Greater stability is achieved when the outer energy level is fully occupied by electrons (usually 8) - this is the octet rule. Ion formation occurs according to this rule Example Sodium atom GREATER Sodium ion STABILITY Na Na+ 1 electron is lost Note: Inert gases are stable because the outer level is fully occupied by electrons Monday, 3 May 2010
    • ELECTRON PAIRS AND ELECTRON SPINS “MORE THAN YOU NEED TO KNOW!!” Electron spins cause magnetic moments. Think of a magnetic moments as being like a tiny magnet Monday, 3 May 2010
    • ATOM MODELS Models are used to explain things that we can’t see and/or understand. Showing only the outer electrons (valence electrons) is a useful model. Examples - “electron dot diagrams” Electron configuration is 2.5 but only the 5 valence electrons N are shown (the 7 protons and 7 neutrons are not shown in this model) Electrons are displayed as dots and shown in pairs as they are thought to occupy the same region in an energy level. Cl Monday, 3 May 2010
    • “CAN YOU SEE THE PATTERN?” Metal Key Borderline but more non - metal Non - metal “Which atoms will bond covalently to form molecules?” Monday, 3 May 2010
    • COVALENT BONDING Covalent bonds are formed between non-metal atoms. The bond is based on the mutual attraction of 2 different positively charged nuclei to the same pair of negatively charged electrons. Molecules are formed. Example: Chlorine, Cl2 Chlorine does not normally exist as individual atoms. Two chlorine atoms pair up to make a molecule. A pair of electrons is shared between the two atoms: Each chlorine atom 7 valence Cl + Cl Cl Cl now has 8 valence electrons electrons A lone pair of electrons A shared pair “The octet rule is nearly always obeyed except where Hydrogen is involved in a covalent bond. The outer energy level of hydrogen is fully occupied when it contains 2 electrons. Hydrogen obeys the duet rule” Monday, 3 May 2010
    • LEWIS STRUCTURES The chlorine molecule drawn (above) is an example of a Lewis structure Other Lewis structures Water H2O O H H Hydrogen chloride HCl H Cl Note Both the octet and duet rules are both obeyed in the examples (above) The attraction between atoms is called a bond A bond can be drawn as a line: H H - Cl O O Ex 5A Q.1 to 3 - answers only Monday, 3 May 2010
    • LEWIS STRUCTURES II DOUBLE & TRIPLE BONDS Monday, 3 May 2010
    • DOUBLE BONDS Sometimes, in order to obey the octet rule, two atoms will need to share two pairs of electrons. This TWO shared pair of electrons forms the basis of a double bond. Examples Silicon dioxide, SiO2 contains 2 double bonds O Si O O Si O TWO pairs are shared The octet rule is satisfied for each atom Carbon tetrachloride CCl4 contains only in the molecule single bonds Cl Cl Cl C Cl Cl C Cl Cl Cl Monday, 3 May 2010
    • TRIPLE BONDS When three pairs of electrons are shared, a triple bond is formed. Example Propyne, C3H4 H H C C C H H THREE pairs are shared Note • Two atoms joined by a double bond are closer together than two atoms joined by a single bond. The double bond is shorter and stronger but allows the molecule to be more reactive because there are more electrons concentrated there. • The same applies for a triple bond compared to a double bond. Monday, 3 May 2010
    • DIFFICULT LEWIS STRUCTURES Monday, 3 May 2010
    • RESONANCE STRUCTURES Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this H H C C C H H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H H C C C H H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs This carbon does not have an octet !!! Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • PROCESS FOR DRAWING LEWIS STRUCTURES 1. Add up the total number of electrons 2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet rule is obeyed for these atoms 3. Any lone pairs left over should then be placed around the central atom/s. 4. If you find that the central atom/s does not have an octet then use double or triple bonding to achieve this Step 1: 16 electrons in total H Step 2: Placing the electron pairs around H C C C H the outer atoms. (They will all be bonding pairs in this case). H There are now 8 remaining pairs This carbon does not have an octet !!! Step 3: Step 4 Placing the remaining pairs around We will need to use a triple bond on this the central atoms. carbon to give it an octet. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” H H C C C H H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H H C C C H H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • “Try again .... and this time GET IT SORTED” Step 1: 16 electrons in total H Step 2: Placing the electron pairs around the outer atoms. (They will all be H C C C H bonding pairs in this case). H There are now 8 remaining pairs THREE pairs are shared Step 3: Placing the remaining pairs around the central atoms. Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Br Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 Br Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O H H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 H H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Step 3 Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Step 3 But carbon doesn’t have an octet !! Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Step 3 But carbon doesn’t have an octet !! Step 4 Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • EXAMPLES Draw Lewis structures for the following: (a) PBr3 Step 1 26 electrons Br Step 2 Br P Step 3 Br (b) CH2O Step 1 12 electrons H Step 2 H C O Step 3 But carbon doesn’t have an octet !! Step 4 Ex 5A Q.4 & 5 - answers only Monday, 3 May 2010
    • IONIC SOLIDS Monday, 3 May 2010
    • IONIC SOLIDS Monday, 3 May 2010
    • IONIC BONDING Ionic bonds are formed between metal and non-metal ions. The bond is based on the attraction between positively and negatively charged ions. Ionic compounds are formed. Cl- Na+ Cl- “Negative ions are called anions” Na+ Cl- Na+ “Positive ions are Cl- Na+ Cl- called cations” Note • Because they are oppositely charged, Sodium and Chloride ions are attracted to each other. • This attraction extends in 3 dimensions and results in a huge cubic arrangement of ions. This arrangement is called a lattice. Ex 6A Q.1 to 5 - answers only Monday, 3 May 2010
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    • This is Ann Ion. Monday, 3 May 2010
    • This is Ann Ion. She’s unhappy and negative. Monday, 3 May 2010
    • + + This is Ann Ion. She’s unhappy and negative. Monday, 3 May 2010
    • + + This is Ann Ion. This is a cat-ion. She’s unhappy and negative. Monday, 3 May 2010
    • + + This is Ann Ion. This is a cat-ion. She’s unhappy and He’s a “plussy” cat! negative. Monday, 3 May 2010
    • PERIODIC TRENDS Monday, 3 May 2010
    • THE PERIODIC TABLE (numbers given to columns) 3 4 (numbers given to rows) Key: show relative atomic size. Size increases across a row & decreases down a column. Note • There are columns of less reactive metals (transition elements) between groups 2 and 13 • The dotted line separates metals from non-metals Monday, 3 May 2010
    • REACTIVITY OF METALS The reactivity of a metal is a measure of the metal’s ability to participate in a chemical reaction. Metals react when their atoms lose their valence electrons. The easier the electrons are lost, the more reactive they will be. Decreasing reactivity As we move down As we move across a the group the Li Be period (left to valence electrons get Lithium Beryllium right),the positive Increasing reactivity further from the 2.1 2.2 nucleus increases in nucleus so they charge so the become easier to attractive force on remove. Na Mg Al the valence electrons Sodium Magnesium Aluminium increases. Valence 2.8.1 2.8.2 2.8.3 electrons become Highly more difficult to reactive Ca remove. K Potassium Calcium 2.8.8.1 2.8.8.2 Monday, 3 May 2010
    • REACTIVITY OF NON-METALS The reactivity trends of non-metals can be explained by the ease with which they can gain electrons to form ions. As we move across a period (left to right),the size of the atom decreases so the attractive force on valence electrons increases. Electrons are gained more easily. He Increasing reactivity Helium 2 Highly B C N O Ne Decreasing reactivity reactive Boron Carbon Nitrogen Oxygen F Neon Fluorine 2.3 2.4 2.5 2.6 2.7 2.8 Si P S Cl Ar Silicon Phosphorus Sulphur Chlorine Argon 2.8.4 2.8.5 2.8.6 2.8.7 2.8.8 As we move down the group the atoms increase in size as the number of energy levels increases. It Ex 7A & 7B becomes more difficult to gain electrons. Monday, 3 May 2010
    • PHYSICAL PROPERTIES Monday, 3 May 2010
    • Ionic vs covalent FORMULAE Comparing & contrasting Examples: Sodium Chloride, NaCl and Carbon dioxide, CO2 O C O Cl- Na+ Cl- • a molecule - a small particle Na+ Cl- Na+ • a group of atoms joined. 2 atoms of oxygen joined to 1 atom of carbon Cl- Na+ Cl- O C O • a lattice (a huge group of positive and negative ions joined to each other in an organised The formula for an ionic compound way) has quite a different meaning to the • Sodium and chloride ions are formula for a covalently bonded present in a 1:1 ratio compound. Monday, 3 May 2010
    • Ionic vs covalent PHYSICAL PROPERTIES Comparing & contrasting Properties Sodium Chloride Carbon Explanation dioxide State White solid at Colourless Ionic compounds are formed by the strong room gas attraction between positive and negative ions. This makes it difficult to separate the ions temperature by heating the compound so most ionic compounds are solid at room temperature. Melting high low Covalently bonded compounds usually have point very weak forces of attraction between molecules since each molecule is neutral. Separating the particles (molecules) is easy. Most of them are already separated at room temperature (making them solids or liquids). Solubility in High low Solubility requires water molecules to surround water each particle of a compound. Water molecules have a positive end and a negative end. The water molecule’s negative end will be attracted to a positive ion and its positive end to a negative ion. Because molecules are uncharged this attraction to water molecules does not take place. Electrical None when solid None An electric current is the flow of charged conductivity but conducts particles. Ionic solids contain charges that can be free to move and so can conduct electricity. well when in the Covalently bonded compounds can not because molten state or they consist of molecules that are neutral. when in solution Monday, 3 May 2010
    • ESA EXERCISES Monday, 3 May 2010
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