The atomic number of the element having maximum number of unpaired $3p$ electrons is (in ground state) :

The correct option is A $15$
The atomic number of the element having maximum number of unpaired 3p electrons is (in ground state) is 15. In 3p orbital, a maximum of 3 unpaired electrons are possible. The electronic configuration of the atom is $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$.
The atomic number is $2+2+6+2+3=15$.
The element is phosphorous.