Multiple Choice
Which of the following is the correct electron configuration for silicon (Si)?
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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 As^{3+} cation?
A
[Kr] 5s^2 4d^{10} 5p^3
B
[Ar] 4s^2 3d^{10} 4p^3
C
[Ar] 4s^2 3d^{10} 4p^6
D
[Ar] 4s^2 3d^{10} 4p^0
Verified step by step guidance1
Identify the atomic number of arsenic (As), which is 33, meaning a neutral As atom has 33 electrons.
Write the electron configuration for neutral As: $[Ar] 4s^2 3d^{10} 4p^3$.
Since the ion is As$^{3+}$, it has lost 3 electrons compared to the neutral atom, so subtract 3 electrons from the neutral configuration.
Remove electrons first from the outermost shell (highest principal quantum number), which is the 4p orbital, then from 4s if needed.
After removing 3 electrons from the 4p orbital (which originally has 3 electrons), the configuration becomes $[Ar] 4s^2 3d^{10} 4p^0$, representing the As$^{3+}$ cation.
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