1. Periodic Properties of
Chapter 8
Periodic Properties of
the Elements

2. For an atom, electrons are in atomic orbitals.
Energy of an atomic orbital

3. Orbital Energy Levels for the Hydrogen Atom
H atom: E only depends on n
degenerate

4. E depends on n and l same n, l↑ ↔ E↑ Chapter 8, Figure 8.6
General Energy Ordering of Orbitals for Multielectron Atoms
E depends on n and l
same n, l↑ ↔ E↑

6. A Picture of the Spinning Electron

7. Chapter 8, Figure 8.2
The Stern–Gerlach Experiment

8. Spin quantum number ms
ms = +1/2 or −1/2
4 quantum numbers are used to specify an electron.
How do electrons fill up atomic orbitals?

9. Pauli Exclusion Principle
In a given atom, no two electrons can have the same
set of four quantum numbers.
An orbital can hold only two electrons, they must have
opposite spins.

11. 1s1 2s1 2p1 H atom electron configuration Lowest energy: ↑
ground state ↑ 1s
2s1 ↓ 2s
Excited states
2p1 ↑ 2p
orbital diagram

12. Now we can write the ground state electron
configurations and draw orbital diagrams according
to Pauli principle.
Electron configurations explain many chemical
properties.

13. Chapter 8, Figure 8.6
General Energy Ordering of Orbitals for Multielectron Atoms

15. Chapter 2, Figure 2.13
The Periodic Table: Main-Group and Transition Elements

16. Hund’s rule For degenerate orbitals, the lowest energy is attained
when the number of electrons with the same spin is
maximized.
Valence electrons: electrons in the outermost shell for
main group elements.
They are involved in bonding and reactions.
Core electrons: inner electrons

17. Chapter 8, Figure 8.7
Outer Electron Configurations of the First 18 Elements in the Periodic Table

18. Elements in the same group have similar valence
electron configuration — similar chemical properties.
Number of valence electrons = main group number
Number of filled shells = period number
Noble gases have 8 (He 2) valence electrons. Stable
structure.
Metals: tend to lose valence electrons to reach 8(2)
valence electron.
Nonmetals: tend to gain electrons to reach 8(2) valence
electrons.

20. Review Problem Set 10

22. Chapter 2, Figure 2.13
The Periodic Table: Main-Group and Transition Elements

23. Chapter 8, Figure 8.8
The s, p, d, and f Blocks of the Periodic Table

25. Periodic trends in atomic properties
• Atomic radius

26. Atomic Radii (in Picometers) for Selected Atoms

27. Atomic radius In a period: decreases from left to right
In a group: increases from top to bottom

28. (a) N or F (b) C or Ge (c) N or Al (d) Al or Ge
EXAMPLE 8.5 Atomic Size
On the basis of periodic trends, choose the larger atom in each pair (if possible). Explain your choices.
(a) N or F (b) C or Ge (c) N or Al (d) Al or Ge

29. Chapter 2, Figure 2.13
The Periodic Table: Main-Group and Transition Elements

30. Choose the larger atom or ion from each pair.
EXAMPLE 8.7 Ion Size
Choose the larger atom or ion from each pair.
(a) S or S2– (b) Ca or Ca (c) Br– or Kr

31. Periodic trends in atomic properties
• Atomic radius
• Ionization energy

32. Ionization energy Energy required to remove an electron from
a gaseous atom or ion.
X(g) → X+(g) + e−
first ionization energy
X+(g) → X2+(g) + e−
second ionization energy

33. Chapter 8, Figure 8.15
First Ionization Energy versus Atomic Number for the Elements through Xenon

34. Ionization energy In a period: increases from left to right
In a group: decreases from top to bottom
(general trend)

36. Periodic trends in atomic properties
• Atomic radius
• Ionization energy
• Electron affinity

37. Electron affinity Energy change associated with the addition
of an electron to a gaseous atom.
X(g) + e− → X−(g)
X(g) + e−
X−(g) E Ei Ef
stable X−
∆E = Ef − Ei = EA < 0

38. Chapter 8, Figure 8.17
Electron Affinities of Selected Main-Group Elements

39. Electron affinity In a period: increases from left to right
In a group: no clear trend
(very rough trend)

40. Periodic trends in atomic properties
• Atomic radius
• Ionization energy
• Electron affinity
Remember the trends

41. Chapter 2, Figure 2.13
The Periodic Table: Main-Group and Transition Elements

42. Problem Set 11