how to fill electronic configuration of element in the form ns2 ns1 like thatand alsohow to pair the electrons

Electrons possess orbitals of the most minimal vitality accessible. There can be a greatest of just two electrons in any given orbital. No two electrons in a similar particle may have every one of the four quantum numbers alike. This is an announcement of the Pauli Exclusion Principle. 

Electrons are included by progressively filling subshells with electrons in a particular request in light of expanding energies of the subshells. 

The most extreme number of electrons in any s subshell is two. 

The greatest number of electrons in any p subshell is six. 

The most extreme number of electrons in any d subshell is ten. 

The most extreme number of electrons in any f subshell is fourteen.