1. Complete the following table. Z eff Atomic orbital designation for highest en

Question

1. Complete the following table.

Zeff

Atomic orbital designation
for highest energy
valence electron (i.e., 2s)

Ge

C

2. Which atom (Ge or C) has the smaller first ionization energy? Enter the chemical symbol in the space provided.

3. Which one of the following statements best explains the trend observed in part 2?

A. Ionization energy increases down a group. The valence electrons occupy a higher energy atomic orbital, thereby requiring more energy to remove the valence electron.
B.Ionization energy decreases down a group. Elements lower in a group have larger atomic radii. The valence electrons are further from the nucleus so that the attraction between the valence electrons and nucleus is decreased and the energy required to remove the valence electrons is less.
C. Ionization energy decreases to the right across a period. Within a period the increasing number of valence electrons result in stronger electron-electron repulsion thereby decreasing the amount of energy required to remove the valence electrons.
D. Ionization energy increases to the right across a period. Within a period valence electrons of elements to the right have a larger Zeff and therefore feel a stronger attraction to the nucleus, requiring more energy to remove the valence electrons.

Element

Zeff

Atomic orbital designation
for highest energy
valence electron (i.e., 2s)

Ge

C

Explanation / Answer

For the last electron of Ge, (electron in the 4p shell)

(1s)2 (2s 2p)8 (3s 3p)8 (3d)10 (4s 4p)3

Shielding Contribution from (4s 4p)3 is 3*0.35= 1.05

Shielding Contribution from (3d)10 is 10*0.85= 8.5

Shielding Contribution from (3s 3p)8 is 8*0.85= 6.8

Shielding Contribution from (2s 2p)8 is 8*1.0= 8.0

Shielding Contribution from (1s)2 is 2*1.0= 2

Total Shielding constant 26.35, hence Zeff is (32-26.35)= 5.65

2) Ge being a 4th period element it has higher atomic radii than Carbon. So, the last electron of Ge will be far from nucleus compared to than that of Carbon. Thus, Ge has the smaller first ionization energy.

3) Option B & Option D

Element Zeff Atomic orbital designation
for highest energy
valence electron (i.e., 2s) Ge 5.65 4p C 2.55 2p

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