Which of the following electronic configurations represents an excited state of a neutral carbon atom?

Solution

1. The ground state configuration of carbon is $1s^{2}2s^{2}2p^2$.
2. An excited state occurs when an electron is promoted to a higher energy level.
3. Configuration $1s^{2}2s^{2}2p^{1}3s^1$ has the same number of electrons as carbon.
4. This configuration represents an electron promoted from the $2p$ to the $3s$ orbital.
5. Hence the answer is (B).