Phosphorus has an atomic number 15. As the number of protons in sulfur is 15, there are 15 electrons in orbit around the nucleus.
Electrons revolve around the nucleus of an atom and are found in shells which consist of sub shells. The nth shell can have a total of 2*n^2 electrons. Each shell is made up of sub shells and a shell with nay value of n can have n number of sub shells that have are given a value l = 0, 1, 2, 3... (n - 1) that correspond to s, p, d, f... sub shells. For any value of l, the sub shell can have 2(2l + 1) electrons.
The first shell has only one sub shell which has an l value of 0 and is the s sub shell. The second shell has 2 sub shells, s and p and can accommodate 8 electrons. The third sub shell has 3 sub shells s p and d.
For phosphorus, the first shell has 2 electrons, the second shell has 8 electrons and the third shell has 5 electrons.
The electron configuration of phosphorus is 1s2, 2s2, 2p6, 3s2, 3p3
The noble gas configuration is the configuration of the electrons in excess to the number of electrons in the noble gas with an atomic number just less than the element. For phosphorus, this gas is Neon.
The noble gas configuration of phosphorus is [Ne], 3s2, 3p3