CHM 501

11. Plot electron affinity and Z* (calculated using Slater's rules) as a function of atomic number for the atoms from Li to Ne. In general, does Z* account for the variation in electron affinity? Why or why not? Are there any specific anomalies in the trend? If so, give an explanation.

Answer

Element

Electron Configuration

Z* (Calculated)

Electron Affinity (eV)

Li

(1s2)(2s1)

3 – [2(0.85)] = 1.30

0.618

Be

(1s2)(2s2)

4 – [2(0.85) + 1(0.35)] = 1.95

–0.5

B

(1s2)(2s22p1)

5 – [(2(0.85) + 2(0.35)] = 2.60

0.277

C

(1s2)(2s22p2)

6 – [2(0.85) + 3(0.35)] = 3.25

1.263

N

(1s2)(2s22p3)

7 – [2(0.85) + 4(0.35)] = 3.90

–0.07

O

(1s2)(2s22p4)

8 – [2(0.85) + 5(0.35)] = 4.55

1.461

F

(1s2)(2s22p5)

9 – [2(0.85) + 6(0.35)] = 5.20

3.399

Ne

(1s2)(2s22p6)

10 – [2(0.85) + 7(0.35)] = 5.85

–1.2

Generally, Z* and EA give the same trend. However, N and Ne are very low: N is half-filled and Ne is filled, neither want to remove this stability and add an electron. Li is a bit high perhaps, maybe because the product anion is a filled shell.