What electron configuration repreents the first excited state of phosphorus? A. 1s2 2s2 2p6 3s2 3p2 4s1
B. 1s2 2s2 2p6 3s2 3p4
C. 1s2 2s2 2p6 3s1 3p4
D. 1s2 2s2 2p6 3s2 3p3 4s1
E. 1s2 2s2 2p6 3s2 3p3

Option C:

1s2 2s2 2p6 3s1 3p4

Explanation:

At a ground level, Phosphorous has an electronic configuration of 1s2 2s2 2p6 3s2 3p3 (using the spdf notation).

Once the atom becomes excited, an electron from the 3s sub-level will gain energy and jump over to the 3p sub-level, making the configuration 1s2 2s2 2p6 3s1 3p4.

The number of electrons at the 3p sub-level will now become 4 because of the addition of the new electron while the number of atoms at the 3S sub-level will reduce to 1 because an electron left this sub-level.

law of conservation of matter