Write out the complete electron configuration for Cu, Cu
and Cu
according to the normal pattern of filling electrons. (3 points) (b) Rewrite the electron configurations for Cu and Cu
promoting one electron to get a more stable configuration. (2 points) 7. Element Q, in the fourth period, has the following ionization energies:
=590 kJ,
=1145 kJ,
=4912 kJ,
=6491 kJ,
=8140 kJ,
=10,500. What is element Q? Explain briefly. (2 points) 8. Nitrogen is a nonmetal that \”likes\” to gain electrons. However, its electron affinity is +7.0 kJ. Explain what the positive value indicates. Use the electron configuration to explain why it is it is positive for nitrogen. (2 points)
The Correct Answer and Explanation is:
(a) Complete Electron Configurations (normal filling pattern):
- Cu (Copper):
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹ - Cu⁺ (Copper I ion):
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁹ - Cu²⁺ (Copper II ion):
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹
(b) More Stable (Promoted) Configurations:
- Cu:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
One electron from 4s is promoted to 3d to make 3d a full sublevel, which is more stable. - Cu⁺:
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰
Loss of the single 4s electron from neutral copper results in a stable, fully filled 3d sublevel.
7. Element Q Identification:
The ionization energies are:
- IE₁ = 590 kJ/mol
- IE₂ = 1145 kJ/mol
- IE₃ = 4912 kJ/mol
- IE₄ = 6491 kJ/mol
- IE₅ = 8140 kJ/mol
- IE₆ = 10,500 kJ/mol
There is a significant jump between IE₂ and IE₃, indicating the removal of a core electron after two valence electrons have been removed. This pattern is characteristic of magnesium (Mg), which has two valence electrons in the 3s orbital. Therefore, element Q is magnesium.
8. Positive Electron Affinity of Nitrogen:
Electron affinity refers to the energy change when an atom gains an electron. For nitrogen, the value is +7.0 kJ/mol, which means energy must be added for nitrogen to accept an additional electron. This is unusual for a nonmetal.
Nitrogen’s electron configuration is:
1s² 2s² 2p³
Its 2p sublevel is half-filled, which is relatively stable due to minimized electron repulsion. Adding another electron would increase repulsion in the already half-filled 2p orbital. As a result, nitrogen resists gaining an extra electron and requires energy input, explaining the positive electron affinity.
