Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy?

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According to the aufbau principle, electrons fill subshell in order of lowest available energy. Electrons normally fill subshells in this order:

$$ 1s \rarr 2s \rarr 2p \rarr> 3s \rarr 3p $$

In the last choice, an electron is present in \(3p\) despite \(3s\) having a slot for an electron. This implies that the electron is in an excited state. Typically, this doesn't last a long time, and the electron will fall back down to the ground state, releasing energy in the process.