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Utilizing theperiodictable Utilizing theperiodictable Document Transcript

  • AP Chemistry Rapid Learning Series - 13 Rapid Learning Center Chemistry :: Biology :: Physics :: Math Rapid Learning Center Presents … p g Teach Yourself AP Chemistry Visually in 24 Hours 1/58 http://www.RapidLearningCenter.com The Periodic Table and Chemical Periodicity AP Ch i t R id Learning Series Chemistry Rapid L i S i Wayne Huang, PhD Kelly Deters, PhD Russell Dahl, PhD Elizabeth James, PhD Debbie Bilyen, M.A. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com Rapid Learning Center www.RapidLearningCenter.com/ © Rapid Learning Inc. All rights reserved. 1
  • AP Chemistry Rapid Learning Series - 13 Learning Objectives By completing this tutorial you will learn… The organization of the periodic table. table How properties of an element can be determined from trends of the periodic table. How electronegativity, ionization energy electron energy, affinity relate to atomic radii. How ionic radii relates to atomic radii. 3/58 Concept Map Previous content Chemistry New content Studies Matter One type of is Periodic Table Organized on Elements Atomic Mass Used to predict properties of elements according to trends Atomic Radii Electronegativity Ionization Energy Electron Affinity Ion Charge & Radii 4/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 2
  • AP Chemistry Rapid Learning Series - 13 History of the Periodic Table 5/58 Development of the Modern Table Scientists went through many revisions to arrive at the current Periodic Table. Many scientists organized the elements in different ways. Mendeleev organized the elements by atomic mass in rows/columns g p p according to properties. Some holes were left if no known element had the properties needed to fit p the pattern. More elements were discovered. 6/58 These systems had various flaws. The holes were filled in. Elements were reorganized by atomic number. A couple of elements switched places. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 3
  • AP Chemistry Rapid Learning Series - 13 Organization of the Periodic Table of Elements 7/58 Definition: Periodic Table Periodic Table – A tool used by chemists. Organizes the elements and provides information about them. Elements are organized by increasing order of atomic number. The atomic number is the number of protons and determines the identity of the atom. 8/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 4
  • AP Chemistry Rapid Learning Series - 13 Groups and Periods The periodic table is organized by: Periods Rows are called “periods” Groups Columns are called “groups” or “families” groups families 9/58 Information for Each Element Most periodic tables give the following information, but it can be in a different location. Element Symbol If there’s a second letter, it’s lowercase. Atomic Mass Number with decimals. Give the mass for 1 mole of atoms. 12 C Carbon C b 12.01 Atomic Number Whole Wh l number— b elements are ordered by this on the periodic table. Element Name El tN 10/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 5
  • AP Chemistry Rapid Learning Series - 13 Metals and Non-Metals The stair-step separates the metals & non-metals. Metalloids touch the stair-step. Most active non-metals non metals Most active metals 11/58 Properties of Metals and Non-Metals There are several characteristics of each type of element: Metals Non-Metals High electrical conductivity Low electrical conductivity High melting points Low melting points Malleable & ductile Metalloids Brittle Bi l Have properties of both metals and nonmetals 12/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 6
  • AP Chemistry Rapid Learning Series - 13 How to Memorize the Elements 1-20 13/58 Mnemonic for the First 20 Elements Happy H H Henry, Th Li l B The Little Beach B h Boy, C N dO FiN CaN FiNe; Naughty Megan, the Alpine Sister, Pretends to Ski at ClArK Canyon 14/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 7
  • AP Chemistry Rapid Learning Series - 13 Periodicity 15/58 Definition: Periodicity Periodicity of the Periodic Table – The predictable pattern by which properties of elements change across or down the l t h d th periodic table. There are always exceptions to these periodicity trends… each of the trends is a “general” trend as you move across a period or down a group. 16/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 8
  • AP Chemistry Rapid Learning Series - 13 Atomic Mass 17/58 Definition: Atomic Mass Atomic Mass – the mass in grams for 6.02 × 1023 atoms. Found on the periodic table. 18/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 9
  • AP Chemistry Rapid Learning Series - 13 Atomic Mass Trends In general, the atomic mass: Increases Increases 19/58 Atomic Mass Trends Reasoning Why does atomic mass increase across a period? Moving left to right, the number of protons, neutrons and electrons all increase. More subatomic particles leads to higher mass. M b t i ti l l d t hi h Why does atomic mass increase down a group? For the same reason as above! e e n p n p n p e Move across the periodic table Mass increases Lithium atom e e pn p p nn p n e e Beryllium atom 20/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 10
  • AP Chemistry Rapid Learning Series - 13 Atomic Radii 21/58 Definition: Atomic Radius Atomic Radius – Half of the distance between the nuclei of two bonded b t th l i ft b d d atoms. H H Distance between nuclei Atomic radius of hydrogen atom 22/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 11
  • AP Chemistry Rapid Learning Series - 13 Atomic Radii Trends In general, atomic radii: Decreases Increases 23/58 Atomic Radii Trends Reasoning - 1 Why does atomic radii decrease across a period? Moving left to right, the number of protons, neutrons and electrons all increase. e e e n p n p n p e Move across the periodic table Radius decreases Lithium atom e e pn p p p n n n e Beryllium atom As the # of protons and electrons increase, the attraction between the positive nucleus and negative electron cloud increases. This attraction “pulls” in on the electrons. 24/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 12
  • AP Chemistry Rapid Learning Series - 13 Atomic Radii Trends Reasoning - 2 Why does atomic radii increase down a group? Protons, neutrons and electrons are also added as you move down a group. e e Move down the periodic table e + e e Radius increases e e e e e + e e e e Lithium atom Sodium atom However, the electrons are added in new energy levels. 25/58 The inner electrons “shield” the new outer electrons from the pull of the nucleus, therefore it doesn’t pull in like the last slide. Electronegativity 26/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 13
  • AP Chemistry Rapid Learning Series - 13 Definition: Electronegativity Electronegativity – The pull an atom has on the electrons it shares in a bond with another atom. 27/58 Electronegativity Trends In general, electronegativity: Increases Decreases 28/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 14
  • AP Chemistry Rapid Learning Series - 13 Electronegativity Trends Reasoning - 1 Why does electronegativity increase across a period? Moving left to right, the radius of the atom decreases as more protons pull on more electrons. Move across the periodic table e e n p n p n p e e e pn p p p n n n Radius decreases e Electronegativity increases Lithium atom e Beryllium atom When an atom is smaller, the electrons are closer to the nucleus, and therefore feel the pull more strongly. Smaller atoms will have a higher electronegativity. 29/58 Electronegativity Trends Reasoning - 2 Why does electronegativity decrease down a group? As you move down a group, the radius increases as more electrons shells are added added. e e e + Move down the periodic table e e Radius increases Electronegativity decreases e e e e e + e e e e Lithium atom Sodium atom As the outer electrons (those involved in bonding) are farther from the nucleus, they will feel the “pull” of the nucleus less. 30/58 Larger atoms have lower electronegativity. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 15
  • AP Chemistry Rapid Learning Series - 13 Ionization Energy 31/58 Definition: Ionization Energy Ionization energy – The energy needed to remove the outermost electron. 32/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 16
  • AP Chemistry Rapid Learning Series - 13 Ionization Energy Trends In general, Ionization Energy: Increases Decreases 33/58 Ionization Energy Trends Reasoning - 1 Why does Ionization Energy increase across a period? Moving left to right, the radius of the atom decreases as more protons pull on more electrons. Move across the periodic table e e n p n p n p e e e Radius decreases IE increases Lithium atom e pn p p p n n n e Beryllium atom When an atom is smaller, the electrons are closer to the nucleus, and therefore feel the pull more strongly. It is harder to pull electrons away from these smaller atoms. 34/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 17
  • AP Chemistry Rapid Learning Series - 13 Electronegativity Trends Reasoning - 2 Why does electronegativity decrease down a group? As you move down a group, the radius increases as more electrons shells are added added. e e Move down the periodic table e + Radius increases IE decreases e e e e e e e + e e e e Lithium atom Sodium atom As the outer electrons (those involved in bonding) are farther from the nucleus, they will feel the “pull” of the nucleus less. 35/58 It is easier to remove an electron from a larger atom. Electron Affinity 36/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 18
  • AP Chemistry Rapid Learning Series - 13 Definition: Electron Affinity Electron Affinity – The energy released when an electron is added to an atom. 37/58 Electron Affinity Trends In general, electron affinity: Increases Decreases 38/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 19
  • AP Chemistry Rapid Learning Series - 13 Electron Affinity Trends Reasoning - 1 Why does Electron Affinity increase across a period? Moving left to right, the radius of the atom decreases as more protons pull on more electrons. Move across the periodic table e e n p n p n p e e e pn p p p n n n Radius decreases e EA increases Lithium atom e Beryllium atom When an atom is smaller, the electrons are closer to the nucleus, and therefore feel the pull more strongly. 39/58 A smaller atom can handle an extra electron more easily as it can be more “controlled” by the closer nucleus. Electron Affinity Trends Reasoning - 2 Why does electron affinity decrease down a group? As you move down a group, the radius increases as more electrons shells are added. e e e + Move down the periodic table Radius increases EA decreases e e e e e e e + e e e e Lithium atom Sodium atom As the outer electrons (those involved in bonding) are farther from the nucleus, they will feel the “pull” of the nucleus less. 40/58 The larger atom is less able to “control” a new electron added. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 20
  • AP Chemistry Rapid Learning Series - 13 Ionic Charge & Radii 41/58 Definition: Ion Ion – Atom with a charge. Cation – Positively charged ion. Results from loss of electrons. Anion – Negatively charged ion. Results from gain of electrons. 42/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 21
  • AP Chemistry Rapid Learning Series - 13 Predicting Ion Charge Some ion charges can be determined from the element’s placement on the periodic table. Periodic Table - Charges of Common Ions H+ Li + Be 2+ N3- Na + Mg2+ K+ Ca 2+ F- P3- Al3+ O2S2- Cl - Zn2+ Ga 3+ Rb+ Sr2+ Se 2- Br- Ag+ Cd2+ I- Cs+ Ba 2+ Fr+ Ra 2+ 43/58 Ionic Radii - Cations How does the radius of a cation compare to the parent atom? Atoms lose electrons to create positive ions. e e e + Creating a cation, losing electrons Radius decreases Lithium atom e e + Li+ ion When electrons are lost, there are now more protons than electrons. 44/58 Therefore, the protons have a greater “pull” on each of the electrons. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 22
  • AP Chemistry Rapid Learning Series - 13 Ionic Radii - Anions How does the radius of an anion compare to the parent atom? Atoms gain electrons to create negative ions. e e e e e + e e Creating an anion, gaining electrons e e e + Radius increases e e e e e e e Oxygen atom e O2- ion When electrons are gained, there are now more electrons than protons. 45/58 Therefore, the protons have a weaker “pull” on each of the electrons. Trend Summary and Examples 46/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 23
  • AP Chemistry Rapid Learning Series - 13 Summary of Trends In general: Atomic Mass: Increases Atomic Radii: Decreases Electronegativity: Increases Ionization Energy: Increases Electron Affinity: Increases Atomic Mass: Increases Atomic Radii: Increases Electronegativity: Decreases Ionization Energy: Decreases Electron Affinity: Decreases 47/58 Don’t memorize them all… understand the reasoning behind the atomic radii trend, and know the definitions of the other terms...then you can reason out their trends as well. Example - 1 Example: List Li, Cs and K in increasing order of: These elements are in the same group. A: Atomic radii Li < K < Cs Radii of the atom As you move down a group, electron shells are added. This makes a larger atom. The element at the top will be the smallest. B: Electronegativity Pull an atom has on electrons it shares in a bond. As you move down a group, atoms get larger. The larger the atom, the less pull on the electrons. Cs < K < Li Smallest atom will have the highest electronegativity. C: Ionization Energy Energy needed to remove the outermost electron. electron As you move down a group, atoms get larger. The larger the atom, the less pull on the electrons. Cs < K < Li Smallest atom will have the highest ionization energy. D: Electron Affinity Cs < K < Li 48/58 Energy released when another electron is added. As you move down a group, atoms get larger. The larger the atom, the less pull on the electrons. Smallest atom will have the highest electron affinity. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 24
  • AP Chemistry Rapid Learning Series - 13 Example - 2 Example: Put in order of increasing size: Ca, Ca2+ and Ca+. Cations are formed by removing electrons electrons. When electrons are removed, there are more protons per electron. The pull on each electron from the nucleus is now greater. The cation will be smaller than the parent atom. Ca2+ < Ca+ < Ca 49/58 The Periodic Table & The AP Exam 50/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 25
  • AP Chemistry Rapid Learning Series - 13 Periodicity in the Exam Common periodicity problems: Which property does which trend Definitions of the trends (ionization energy, electron affinity, etc.) Explain properties of elements based on periodic trends (in free response section). 51/58 Multiple Choice Questions The multiple choice periodicity questions tend to be straight-forward. Example: E l As you move down the periodic table from element 3 to element 55, the ionization energy ____. A. B. C. D. E. Increases Decreases Remains constant Increases then decreases Decreases then increases Answer: B. Decreases 52/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 26
  • AP Chemistry Rapid Learning Series - 13 Another Multiple Choice Question Some questions are “definition” type questions. Example: E l The energy needed to remove the outermost electron is ____. A. B. C. D. E. Electron Affinity Activation Energy Ionization Energy Enthalpy of Formation Electronegativity Answer: C. Ionization Energy 53/58 Free Response Questions The Free Response questions often ask for you to explain certain behavior. Example: Explain the following in terms of atomic or molecular structure: A. The second ionization energy of Mg is much lower than the second ionization energy of Na B. The atomic radius of N is greater than O C. The boiling point of H2O is higher than H2S D. The bond angle of NH3 is smaller than NH4+ Periodicity questions are often combined with subquestions asking about properties dependent on bonding theory or intermolecular forces (covered in future tutorials). 54/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 27
  • AP Chemistry Rapid Learning Series - 13 Answering Free Response Questions Be sure to thoroughly EXPLAIN…not just rephrase! Explain the following in terms of atomic or molecular structure: A. The A Th second ionization energy of Mg is much lower than the second d i i ti fM i hl th th d ionization energy of Na Removing the second electron from Na requires removing an electron from a full, more stable electron shell. Removing the second electron from Mg does not. Therefore, it takes more energy to remove the 2nd electron from Na than Mg. B. The atomic radius of N is greater than O 55/58 N has fewer protons and electrons than O, although both use the same highest energy subshell. The fewer protons and electrons in the N atom have less of an attraction as the greater number of protons and electrons in the O (the electrons are in the same energy level and thus no more shielded). Therefore, the radius of the N is larger. Learning Summary Other periodic trends (Electronegativity, Ionization Energy and Electron Affinity) can be reasoned through using the atomic radii trend. The periodic table t bl organizes i the elements by atomic number. The periodic table can be used to determine chemical properties of an element based on periodic trends. Ions gain or lose electrons to form a g charge. Cations are smaller and anions are larger than the “parent” atom. Radii decreases across the periodic table and increases down the periodic table. 56/58 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 28
  • AP Chemistry Rapid Learning Series - 13 Congratulations You have successfully completed the tutorial Periodic Table and Chemical Periodicity Rapid Learning Center 57/58 Rapid Learning Center Chemistry :: Biology :: Physics :: Math What’s N t Wh t’ Next … Step 1: Concepts – Core Tutorial (Just Completed) Step 2: Practice – Interactive Problem Drill Step 3: Recap – Super Review Cheat Sheet Go for it! 58/58 http://www.RapidLearningCenter.com © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 29