Final answer:
Selenium's complete electron configuration is 1s² 2s² 2p¶ 3s² 3p¶ 3d±⁰ 4s² 4p⁴, with the last electron residing in the 4p orbital (4p⁴). Therefore, the correct answer is D) 4p.
Step-by-step explanation:
The complete electron configuration of selenium is as follows: 1s² 2s² 2p¶ 3s² 3p¶ 3d±⁰ 4s² 4p⁴. This indicates that selenium's electrons fill up to the 4p orbital. When looking at the configuration, it can be seen that the orbitals fill up in a specific order, generally starting with the lowest energy orbitals.
Given the choices provided to identify where selenium's last electron resides:
- A) 2s - Incorrect because this is a lower energy level filled earlier in the sequence.
- B) 3p - Incorrect, as this orbital is filled before reaching the fourth energy level.
- C) 4s - Incorrect because the 4s orbital is filled before the 4p orbitals.
- D) 4p - Correct, because the valence electron configuration for selenium ends with 4p⁴, indicating that the last electron added to selenium's configuration occupies the 4p orbital.
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