Multiple Choice
Which of the following represents the correct electron configuration for selenium (Se)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct electron configuration for the arsenide ion, As^{3-}?
A
1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^5
B
1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6
C
1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^3
D
1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^1
Verified step by step guidance1
Identify the atomic number of arsenic (As), which is 33. This means a neutral arsenic atom has 33 electrons.
Since the ion is As^{3-}, it has gained 3 extra electrons, so the total number of electrons is 33 + 3 = 36.
Write the electron configuration for 36 electrons by filling orbitals in order of increasing energy, following the Aufbau principle, Pauli exclusion principle, and Hund's rule.
Recall the order of filling: 1s, 2s, 2p, 3s, 3p, 4s, 3d, then 4p. Make sure to include all electrons up to 36.
Confirm that the final electron configuration corresponds to a full 4p subshell (4p^6), since the extra 3 electrons fill the 4p orbitals beyond the neutral arsenic configuration.
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