Nitride ion in ${\text{Li}}_{\text{3}}\text{N}\left({\text{N}}^{-3}\right)$  is composed of

Nitride ion in ${\text{Li}}_{\text{3}}\text{N}\left({\text{N}}^{-3}\right)$  is composed of 7 protons  $+10$  electrons already nitrogen having 7  electrons and remaining 3  electrons are lost by lithium is gained the nitrogen that 3 electrons (lost by Li) due to high electro negativity of nitrogen. So total protons and electrons in nitride is 7  and 10.