Multiple Choice
According to the aufbau principle, which orbital is filled first when building up the electron configuration of an atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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Given the electron configuration 1s^2 2s^2 2p^3, how many unpaired electrons are present in this atom?
A
0
B
2
C
1
D
3
Verified step by step guidance1
Identify the element or atom based on the given electron configuration: $1s^2\ 2s^2\ 2p^3$.
Recall that the $1s^2$ and $2s^2$ orbitals are fully filled, meaning all electrons in these orbitals are paired.
Focus on the $2p^3$ configuration, which means there are 3 electrons in the three $2p$ orbitals.
Apply Hund's rule, which states that electrons will fill degenerate orbitals (orbitals of the same energy) singly first, with parallel spins, before pairing up.
Since there are 3 electrons in 3 $2p$ orbitals, each electron will occupy its own orbital unpaired, resulting in 3 unpaired electrons.
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