What is the electron configuration of an element with atomic number 15?

Explanation: An element with atomic number 15 means the element has 15 electrons and 15 protons. The given element is Phosphorous and the chemical symbol is P. According to Afbau's rule , the electrons are filed in order of increasing energies as given below:-

The nearest noble gas is Neon(Ne) with 10 electrons. Thus in noble gas configuration it can also be written as:

the answer is b. dilution