Atomic Structure II

Electron Configurations

Barbara A. Gage PGCC CHM 1010

Atomic Orbitals

• Each electron is assigned to:Primary energy level (shell), nOrbital type in the shell (s,p,d,f)Specific orbital of the type

Because of repulsion considerations only 2 electrons can occupy any orbital (spinning in opposite directions)

Barbara A. Gage PGCC CHM 1010

Shell (n)

# s orbita

ls

# p orbita

ls

# d orbita

ls

# f orbita

ls

Total e-

1 1 2

2 1 3 8

3 1 3 5 18

4 1 3 5 7 32

5 1 3 5 7 50

Atomic Shells and Orbitals

Barbara A. Gage PGCC CHM 1010

This diagramshows the energylevels of the atomic orbitals.

Electrons fill orbitals from bottom to top ofthe diagram.

Barbara A. Gage PGCC CHM 1010

dark - filled, spin-paired

light - half-filled

no color-empty

TA pg. 241 A vertical orbital diagram for the Li ground state.

Silberberg, Principles of Chemistry

The electron configuration is written as: 1s22s1

shellorbital

# electrons in orbital

Barbara A. Gage PGCC CHM 1010

Table 8.2

Silberberg, Principles of Chemistry Barbara A. Gage PGCC CHM 1010

Silberberg, Principles of Chemistry Barbara A. Gage PGCC CHM 1010

You can use a chartlike this to determine the electron configuration.

(But there is an easierway.)

Barbara A. Gage PGCC CHM 1010

Figure 8.5

A periodic table of partial ground-state electron

configurations.

Silberberg, Principles of Chemistry Barbara A. Gage PGCC CHM 1010

Figure 8.6 The relation between orbital filling and the periodic table.

Silberberg, Principles of Chemistry Barbara A. Gage PGCC CHM 1010

SAMPLE PROBLEM 8.2

Determining Electron Configuration

PLAN:

SOLUTION:

PROBLEM: Using the periodic table on the inside cover of the text (not Figure 8.12 or Table 8.4), give the full and condensed electrons configurations, partial orbital diagrams showing valence electrons, and number of inner electrons for the following elements:

(a) potassium (K: Z = 19)

(b) molybdenum (Mo: Z = 42)

(c) lead (Pb: Z = 82)

Use the atomic number for the number of electrons and the periodic table for the order of filling for electron orbitals. Condensed configurations consist of the preceding noble gas and outer electrons.

(a) for K (Z = 19)

1s22s22p63s23p64s1

[Ar] 4s1

4s1

condensed configurationpartial orbital diagram

full configuration

There are 18 inner electrons.

3d 4pBarbara A. Gage PGCC CHM 1010

SAMPLE PROBLEM 8.2

continued

(b) for Mo (Z = 42)

1s22s22p63s23p64s23d104p65s14d5 [Kr] 5s14d5

(c) for Pb (Z = 82)

[Xe] 6s24f145d106p2

condensed configurationpartial orbital diagram

full configuration

5s1 4d5

condensed configurationpartial orbital diagram

full configuration 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2

There are 36 inner electrons and 6 valence electrons.

6s2 6p2

There are 78 inner electrons and 4 valence electrons.

5p

Barbara A. Gage PGCC CHM 1010

Configuration for Ions

• What is the electron configuration for Na+?

Na = 1s22s22p63s1

Na+ = 1s22s22p63s1

• What is the electron configuration for Se2-?

Se = 1s22s22p63s23p64s23d104p4

Se2- = 1s22s22p63s23p64s23d104p6

Barbara A. Gage PGCC CHM 1010

Configuration for Ions

• Transitions metals have a twist…Fe = 1s22s22p63s23p64s23d6

Fe2+ = 1s22s22p63s23p64s23d6

Fe3+ = 1s22s22p63s23p64s23d5

Barbara A. Gage PGCC CHM 1010