one
Because of the Law of Formal Charges (which you may not have
covered yet in class), Nitrogen not only wants to achieve the Octet
Rule, but it wants to three of its five electrons to form covalent
bonds, and the remaining two are kept to make one lone pair.
Similarly, each halogen wants one covalent bond and three lone pairs, carbon
wants four covalent bonds (no lone pairs), and hydrogen wants one
covalent bond (no lone pairs.)