Chapter 31 - Atomic Physics - Problems and Conceptual Exercises - Page 1114: 69

Excited state

We know that ground state electronic configuration of the carbon atom is $1s^2 2s^2 2p^2$, but the given electronic configuration is $1s^2 2s^2 2p^1 3s^1$; this shows that the electron in $2p^2$ is excited to a $3s$ state, which is a higher state.