Review grade 9 chemistry

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  • 1. Review of Grade 9 Chemistry Periodic Table Structure of the Atom
  • 2. Quiz: Element Symbols  first 20 elements plus Br and I  transition metals: Sb, As, Bi, Cd, Cr, Co, Cu, Au, Fe, Pb, Mn, Hg, Ni, Pt, Ag, Sn, Ti, Zn
  • 3. Element symbol  Rules for writing the element symbols:  First letter capitalize  Second lower case  Hints to remembering symbols for elements:  Hint 1: applies to hydrogen, boron, carbon, nitrogen, oxygen, fluorine, phosphorus, sulfur, iodine etc.  Hint 2: applies to helium, lithium, beryllium, neon, aluminum, silicon, argon, calcium, bromine etc.  Hint 3: applies to magnesium, chlorine, chromium, manganese, zinc, cadmium, platinum etc.  Hint 4: applies to sodium, potassium, iron, copper, silver, tin, antimony, gold, mercury etc.
  • 4. Periodic Table  Periods: horizontal rows  Families or Groups: vertical columns  Elements in the same family have similar physical and chemical properties
  • 5. Periodic Table
  • 6. Metals  left and centre of the periodic table Transition elements (group 3-12) Inner Transition elements (period 6 & 7)
  • 7. Properties of Metals     conduct heat and electricity ductile and malleable Shiny, often silvery-grey in colour solid at room temperature (except mercury)
  • 8. Non-Metals  right side of the periodic table
  • 9. Properties of Nonmetals  poor conductors of heat and electricity  usually solid or gas at room temperature (only Bromine is a liquid at room temperature)  brittle  dull
  • 10. Metalloids  Metals are separated from non-metals by a staircase of elements called metalloids
  • 11. Properties of Metalloids  properties intermediate between metals and non-metals silicon tellurium
  • 12. Chemical Families
  • 13. Chemical Families  Alkali Metals (Group 1)  soft, silver-grey metals  reacts easily with water  Alkaline Earth Metals (Group 2)  silver-grey metals  harder and less reactive than group 1 metals
  • 14. Chemical Families  Halogens (Group 17)  coloured non-metals  very reactive  Noble Gases (Group 18)  colourless non-metals  odourless  very unreactive (does not combine easily with other atoms)
  • 15. Atom  An atom is the smallest part of an element that has all the element’s properties
  • 16. Atomic Theory  Each element has its own unique kind of atom  Atoms of different elements vary in mass, volume and reactivity
  • 17. Atomic Theory  Atoms are not the smallest particles of matter  Subatomic particles combine together to form atoms  Protons  Neutrons  Electrons
  • 18. Subatomic Particles  Protons have a charge of 1+  Electrons have a charge of 1 Neutrons have a charge of 0 (neutral)  The masses of protons and neutrons are almost 2000 times greater than the mass of electrons
  • 19. Subatomic Particle Summary Particle Proton Neutron Electron Relative Charge Location Influences… Mass
  • 20. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + Neutron 0 Electron -
  • 21. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + 1 Neutron 0 1 Electron - 1/2000
  • 22. Inside an Atom: Nucleus  Protons and neutrons form the core of an atom, called the nucleus  The protons and neutrons are held together by strong forces
  • 23. Atomic Number  The number of protons in an atom is known as its atomic number  Each atom has a unique number of protons and thus each atom has a different atomic number
  • 24. Mass Number  Together the protons and neutrons make up the mass of the atom  The mass number is the sum of the number of protons and neutrons in an atom
  • 25. Inside an Atom: Electron Cloud  Surrounding the nucleus are a series of cloud-like energy levels called shells or orbitals  These shells are occupied by electrons  The electron cloud is 10,000 times larger than the nucleus
  • 26. Inside an Atom Imagine the nucleus to be the size of a golf ball. Then on this scale the first electron shell would be about one kilometer from the golf ball, the second shell about four kilometers, the third nine kilometers etc.
  • 27. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + 1 Neutron 0 1 Electron - 1/2000
  • 28. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + 1 Nucleus Neutron 0 1 Nucleus Electron - 1/2000 Shell
  • 29. Inside an Atom: Charge  When the number of electrons equal the number of protons, the atom is neutral (no charge)  When there are more electrons (-) than protons (+) the charge is negative  When there are less electrons (-) than protons (+) the charge is positive
  • 30. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + 1 Nucleus Neutron 0 1 Nucleus Electron - 1/2000 Shell
  • 31. Subatomic Particle Summary Particle Relative Charge Location Influences… Mass Proton + 1 Nucleus Mass & Charge Neutron 0 1 Nucleus Mass Electron - 1/2000 Shell Charge
  • 32. Bohr Model of the atom  electrons surround the nucleus in shells (or orbital)  each shell has a specific energy level  the innermost shell holds 2 electrons  the next two shells hold 8 electrons  the outermost shell is called the valence shell
  • 33. Bohr Model of the atom  the electrons in the valence shell are called valence electrons
  • 34. Bohr diagrams  a Bohr diagram is an illustration of an atom that shows the arrangement and number of electrons in each shell N 7p 7n S Cl 16p 16n 17p 18n
  • 35. Let’s look at an example…
  • 36. Example: Sulphur atomic number sulfur 16 S 32.065 atomic mass  Gather information from the periodic table to draw the Bohr diagram Atomic number = number of protons = number of electrons (in a NEUTRAL atom) = 16
  • 37. Rules for drawing Bohr diagrams  Place the symbol of the element in the center  Electrons are drawn as far away as possible (e.g. north-south, east-west orientations)  Electrons pair up if there are more than 4  Keep count of the maximum number of electrons per shell (first shell holds 2 electrons, the next two shells hold 8 each)
  • 38. Example: Sulphur  Bohr diagram: first shell: 2 electrons second shell: 8 electrons Atomic number = 16 S third shell: 6 electrons total: 16 electrons In a sulphur atom, the valence shell has 6 electrons
  • 39. What’s wrong with this drawing?  The placement of electrons in the valence shell of this diagram is inaccurate  Electrons need to be as far away as possible.
  • 40. What’s wrong with this drawing? S  The placement of electrons in the valence shell of this diagram is inaccurate  Premature pairing of electrons
  • 41. Create Bohr diagrams for the first 20 elements 2 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
  • 42. Lewis dot diagrams  A drawing of an atom with ONLY it’s valence electrons  Example: Carbon C  Example: Phosphorus P
  • 43. Lewis dot diagrams  If an atom has a full valence shell, no electrons are needed and thus only the element symbol is used  Example: Helium = He
  • 44. Create Lewis dot diagrams for the first 20 elements 2 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
  • 45. Trends in the Periodic Table What trends do you see in the number of valence electrons for each group?
  • 46. Trends in the Periodic Table Group 1 elements have 1 valence electron Group 17 elements has 7 valence electron  All atoms of elements in the same group have the same number of valence electrons  As the group number increases, so do the number of valence electron
  • 47. Trends in the Periodic Table What trends do you see in the number of orbitals for each period?
  • 48. Trends in the Periodic Table Period 2 elements have 2 orbitals Period 3 elements have 3 orbitals  All atoms of elements in the same period have the same number of shells (orbitals)  As the period number increases, so do the number of shells
  • 49. Counting Atoms Terms Terms Definition Affect on atom count Subscript Small number written to the lower right corner after the element symbol. Indicates number of atoms of that element. If there are no numbers, a ‘1’ is assumed. Brackets Surrounds a group of atoms. Used when there is more than one of a group of atoms (e.g. polyatomics) Large number written in front of a molecule. All elements inside a bracket is in multiplies of the subscript written after the bracket. Coefficient Indicates the total number of the molecule. All elements after it would be in multiples of the number.
  • 50. Counting Atoms Terms Terms Example Subscript Na3PO4 Brackets Mg3(PO4)2 Coefficient 2 H2O 3 Mg3(PO4)2 Atom count
  • 51. Counting Atoms Terms Terms Example Subscript Na3PO4 Atom count Na = 3 P=1 O=4 Brackets Mg3(PO4)2 Mg = 3 P=1x2=2 O=4x2=8 Coefficient 2 H2O H=2x2=4 O=1x2=2 3 Mg3(PO4)2 Mg = 3 x 3 = 9 P=1x2x3=6 O=4x2x3= 24