Multiple Choice
Which of the following represents the correct ground-state electron configuration for Ru^{2+} (ruthenium(II))?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct full ground-state electron configuration for the element phosphorus (atomic number 15)?
A
1s^2 2s^2 2p^6 3s^2 3p^5
B
1s^2 2s^2 2p^6 3s^2 3p^6
C
1s^2 2s^2 2p^6 3s^2 3p^3
D
1s^2 2s^2 2p^6 3s^2 3p^1
Verified step by step guidance1
Identify the atomic number of phosphorus, which is 15. This means phosphorus has 15 electrons in its neutral ground state.
Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, and so on.
Fill the orbitals with electrons following the maximum capacity of each: 1s can hold 2 electrons, 2s can hold 2, 2p can hold 6, 3s can hold 2, and 3p can hold up to 6 electrons.
Add the electrons in order until you reach 15 total electrons: 2 in 1s, 2 in 2s, 6 in 2p, 2 in 3s, and the remaining 3 electrons go into 3p.
Write the full electron configuration by combining these values: $1s^2 2s^2 2p^6 3s^2 3p^3$, which corresponds to phosphorus in its ground state.
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