# Question 67208

Feb 7, 2015

Phosphorus is located in group 15 of the periodic table and has an atomic number equal to 15. This means that a neutral phosphorus atom has a total of 15 electrons.

The ground state electron configuration for phosphorus is

$\text{P} : 1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{3}$

I'll use the noble gas shorthand notation from this point on.

"P": ["Ne"] 3s^(2) 3p^(3)

Now, an excited state configuration has one electron promoted from a lower to a higher energy level. Looking at the ground state configuration, you could have one electron from the $\text{3s}$ sub-level promoted to the $\text{3p}$ sublevel. The electron configuration will be

"P": ["Ne"] 3s^(1) 3p^(4)

Another possibility is to have one electron from the $\text{3p}$ sub-level promoted to the $\text{4s}$ sub-level

"P": ["Ne"] 3s^(2) 3p^(2) 4s^(1)

Yet another possibility is to have one electron from the $\text{3p}$ sub-level promoted to the $\text{3d}$ sub-level, skipping the $\text{4s}$ sub-level altogether

"P": ["Ne"] 3s^(2) 3p^(2) 3d^(1)#

Read more on how to determine excited state configurations here:

http://socratic.org/questions/how-do-you-determine-excited-state-electron-configuration