1. Chapter 8 The Periodic Table: Structure and Trends
Chemistry 111/112 Chapter 9
Chapter 8 The Periodic Table: Structure and Trends
Copyright (c) 2003 Thomson Learning Reprinted with permission

2. Electron Configurations and the Periodic Table
Chemistry 111/112 Chapter 9
Electron Configurations and the Periodic Table
The periodic table can be divided into four blocks of elements: elements with highest energy electrons in s, p, d, or f subshells.
The arrangement of the elements in the periodic table correlates with the subshell that holds the highest energy electron.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

3. Example: Electron Configurations
Chemistry 111/112 Chapter 9
Example: Electron Configurations
Using only the periodic table, determine the electron configurations of Al, Ti, Br, and Sr.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

4. Electron Configurations of Anions
Chemistry 111/112 Chapter 9
Electron Configurations of Anions
For anions, the additional electrons fill orbitals following the same rules that applies to atoms.
Cl: [Ne] 3s2 3p5 Cl-: [Ne] 3s2 3p6
As: [Ar] 4s2 3d10 4p3 As3-: [Ar] 4s2 3d10 4p6
Many stable anions have the same electron configuration as a noble gas atom.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

5. Electron Configurations of Cations
Chemistry 111/112 Chapter 9
Electron Configurations of Cations
For the electron configurations of cations, electrons of highest n value are removed first. For cases of the same n level, electrons are first removed from the subshell having highest l.
As: [Ar] 4s2 3d10 4p3 As3+: [Ar] 4s2 3d10
Mn: [Ar] 4s2 3d5 Mn2+: [Ar] 3d5
NOTE: For d-block atoms, the ns electrons are removed before the (n-1)d electrons.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

6. Chemistry 111/112 Chapter 9
Test Your Skill
Write the electron configurations of the following ions: (a) N3- (b) Co3+ (c) K+
Copyright (c) 2003 Thomson Learning Reprinted with permission 7

7. Chemistry 111/112 Chapter 9
Isoelectronic Series
An isoelectronic series is a group of atoms and ions that contain the same number of electrons.
The species S2-, Cl-, Ar, K+, and Ca2+ are isoelectronic – they all have 18 electrons.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

8. Chemistry 111/112 Chapter 9
Atomic Radii
An atomic radius is one half the distance between adjacent atoms of the same element in a molecule.
198/2 = 99
228/2 = 114
Sum = 215
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

9. Size Trends for an Isoelectronic Series
Chemistry 111/112 Chapter 9
Size Trends for an Isoelectronic Series
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

10. Sizes of the Atoms and Their Cations
Chemistry 111/112 Chapter 9
Sizes of the Atoms and Their Cations
Atoms are always larger than their cations.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

11. Sizes of the Atoms and Their Cations
Chemistry 111/112 Chapter 9
Sizes of the Atoms and Their Cations
If an atom makes more than one cation, the higher-charged ion has a smaller size.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

12. Atomic and Ionic Radii Anions are always larger than their atoms.
Chemistry 111/112 Chapter 9
Atomic and Ionic Radii
Anions are always larger than their atoms.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

13. Chemistry 111/112 Chapter 9
Test Your Skill
Identify the larger species of each pair: (a) Mg or Mg2+ (b) Se or Se2-
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

14. Atomic Radii of Main Group Elements
Chemistry 111/112 Chapter 9
Atomic Radii of Main Group Elements
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

15. Chemistry 111/112 Chapter 9
Sizes of Atoms
The sizes of atoms are impacted by the effective nuclear charge felt by the outermost electrons.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

16. Effective Nuclear Charge & Size
Chemistry 111/112 Chapter 9
Effective Nuclear Charge & Size
The sizes of atoms increase going down a group.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

17. Chemistry 111/112 Chapter 9
Sizes of Atoms
The increase in effective nuclear charge causes a size decrease across the period.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

18. Chemistry 111/112 Chapter 9
Test Your Skill
Identify the larger species of each pair: (a) Mg or Na (b) Si or C
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

19. Chemistry 111/112 Chapter 9
Ionization Energy
The ionization energy is the energy required to remove an electron from a gaseous atom or ion in its electronic ground state.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

20. Chemistry 111/112 Chapter 9
Ionization Energies
An atom has as many ionization energies as it has electrons.
Example:
Mg(g) → Mg+(g) + e-
I1 = first ionization energy
Mg+(g) → Mg2+(g) + e-
I2 = second ionization energy
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

21. Trends in 1st Ionization Energies
Chemistry 111/112 Chapter 9
Trends in 1st Ionization Energies
The increase in the effective nuclear charge across a period causes an increase in the ionization energy as you go across that period.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

22. Trends in 1st Ionization Energies
Chemistry 111/112 Chapter 9
Trends in 1st Ionization Energies
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

23. Trends in 1st Ionization Energies
Chemistry 111/112 Chapter 9
Trends in 1st Ionization Energies
The slight dip in ionization energy for O is because the fourth p electron now pairs with another electron, slightly repelling each other.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

24. Trends in First Ionization Energies
Chemistry 111/112 Chapter 9
Trends in First Ionization Energies
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

25. Ionization Energy Trends in Isoelectronic Series
Chemistry 111/112 Chapter 9
Isoelectronic species with the greatest charge in the nucleus will have the largest ionization energy.
For the isoelectronic series S2-, Cl-, and Ar, Ar has the largest ionization energy because it has the most protons in its nucleus.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

26. Chemistry 111/112 Chapter 9
Ionization Energy
Predict which species in each pair has the higher ionization energy.
(a) Ca or As (b) K+ or Ca2+
(c) N or As
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

27. Successive Ionization Energies
Chemistry 111/112 Chapter 9
Successive Ionization Energies
Successive ionization energies always increase because of the increasing hold the nucleus has on remaining electrons.
I1 I2 I3 I4 Mg Al
A much larger increase is seen when an electron comes from a lower-energy subshell.
(all values in kJ/mol)
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

28. Chemistry 111/112 Chapter 9
Test Your Skill
Which element, magnesium or sodium, has the greater second ionization energy?
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

29. Chemistry 111/112 Chapter 9
Electron Affinity
The electron affinity of an element is the energy change that accompanies the addition of an electron to a gaseous atom to form an anion.
A(g) + e- → A-(g)
Electron affinities are generally favorable (exothermic) for elements on the right side of the periodic table.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

30. Electron Affinities Chemistry 111/112 Chapter 9
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

31. Alkali Metals – Group 1A (1)
Chemistry 111/112 Chapter 9
Alkali Metals – Group 1A (1)
The reactivity of the Group 1A metals increases down the group. Their chemistry is dominated by the formation of M+ ions.
2M(s) + H2O(l) → 2MOH(aq) + H2(g)
2M(s) + H2(g) → 2MH(s)
2M(s) + X2(g) → 2MX(s) X = F, Cl, Br, I
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

32. Alkali Metal Reactions with O2
Chemistry 111/112 Chapter 9
Alkali Metal Reactions with O2
Only lithium reacts with O2 to give the expected product, lithium oxide.
4Li(s) + O2(g) → 2Li2O(s)
Sodium reacts mainly to yield sodium peroxide.
2Na(s) + O2(g) → Na2O2(s)
Potassium reacts to yield mixtures of the oxide, peroxide, and superoxide.
K(s) + O2(g) → KO2(s)
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

33. Flame Colors of the 1A Elements
Chemistry 111/112 Chapter 9
Flame Colors of the 1A Elements
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

34. The Alkaline Earth Metals – Group 2A (2)
Chemistry 111/112 Chapter 9
The Alkaline Earth Metals – Group 2A (2)
The Group 2A metals are not as reactive as the Group 1A metals. Reactivity increases down the group, and they all form M2+ ions.
Magnesium alloys are useful in aeronautical applications, where low density and high strength are important.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

35. Flame Colors of 2A Elements
Chemistry 111/112 Chapter 9
Flame Colors of 2A Elements
Calcium
Strontium
Barium
Copyright (c) 2003 Thomson Learning Reprinted with permission 1

36. The Halogens – Group 7A (17)
Chemistry 111/112 Chapter 9
The Halogens – Group 7A (17)
The halogens all exist as diatomic molecules, but they are very reactive.
The reactivity decreases as you go down the group. Their chemistry is dominated by the formation of X- ions.
The interhalogens are compounds formed from different halogens, like IF3 and BrCl.
Copyright (c) 2003 Thomson Learning Reprinted with permission 1