Consider these two electron configurations for neutral atoms L and M. L - 1s22s22p63s2
M - 1s22s22p63s13p1

What is the difference between atom L and atom M?

One of the 2p electrons in L has jumped to an excited state
One of the 3p electrons in L has jumped down to a lower energy state
One of the 3s electrons in M has jumped to an excited stat
One of the 3p electrons in M has jumped down to a lower energy state

The 3p electron in M has jumped down to a lower energy state  

Explanation:

L  - 1s² 2s²2p⁶ 3s²

M - 1s² 2s²2p⁶ 3s3p

L and M have the same number of electrons, so they are atoms of the same element.

Atom M is an excited state of atom L.

Either atom L has been excited to atom M or atom M has dropped to the ground state to form atom L.

A is wrong. Both atoms have two 2p electrons.

B is wrong. Atom L has no 3p electrons.

C is wrong. The 3s electron of atom L is already in its lowest energy state.

i'm assuming that it's c.) red bank..

14 days is the half-life of phosphorus-32