What is the electronic configuration of phosphorus?
(A) 2, 8, 5
(B) 2, 8, 4
(C) 2, 8, 6
(D) 2, 8, 3

Hint: The electronic configuration of an atom or an element described how the free electrons in that element are distributed in the atomic orbitals. There is a standard way of writing the electronic configuration. The electrons are arranged in increasing order of energies.

Complete step by step answer:
Phosphorus is an element with atomic number 15. Atomic number represents the number of electrons and the number of protons in the neutral element. The maximum number of electrons that can be accommodated in a shell is based on the principal quantum number represented by n.So, in phosphorus, the atomic number is 15, so as per Aufbau principle its electronic configuration must be 2,8,5.
Hence, the correct option is (A).
Additional Information:
There is also called Hund’s rule which tells that the order in which electrons are filled in all the orbitals belongs to a subshell.

Note: Aufbau principle is the guiding theorem which states that electrons will occupy the orbitals having the lower energies before getting into higher energy orbitals. The energy of an orbital is calculated by the sum of the principal and the azimuthal quantum numbers. First the electrons fall in n=1 then n=2 and so on. Also, the occupancy is limited by Pauli’s exclusion principle. The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.