Multiple Choice
Which of the following is the correct electron configuration for a neutral nitrogen (N) atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following represents the correct electron configuration for a neutral atom of scandium (atomic number 21)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^3
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^2
D
1s^2 2s^2 2p^6 3s^2 3p^6 3d^3
Verified step by step guidance1
Identify the atomic number of scandium, which is 21. This means a neutral scandium atom has 21 electrons to arrange in orbitals.
Recall the order of filling orbitals according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, then 3d.
Fill the orbitals in order with electrons, remembering that each orbital can hold a maximum of 2 electrons, and p orbitals hold 6 electrons, d orbitals hold 10 electrons.
After filling 1s^2, 2s^2, 2p^6, 3s^2, and 3p^6 (which accounts for 18 electrons), place the remaining 3 electrons in the 4s and 3d orbitals.
Since 4s fills before 3d, place 2 electrons in 4s and 1 electron in 3d, resulting in the electron configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1$.
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