H can only form one bond, carbon can form 4 bonds and N can form three bons, so the H will bond the carbon and this will form a triple bond with N:
H- C (triple bond) N
Now, you must count the valence electrons to see if there are some electrons not forming bonds.
H has one valence electron which is in the H - C bond.
C has four valence electrons which are one in the H - C bond and three in the CN bonds.
N has five valence electrons and it has three of them in the CN bonds, therefore you have to add two electrons (points or other marks) to the N atom.
This is the resultant Lewis structrue:
**
H - C (triple bond) N
Where you have to draw three hyphens to represent the triple bond and include the two ** over the N atom to represent the two electrons that are not forming a bond.
