If you draw lewis structure, central atom (N) will have 1 lone pair and 4 single bonds with Hydrogen. Why can't hydrogen in this ion molecule be able to form hydrogen bonding with other molecules alike? Is it because there's only 1 electron on the central atom? See for yourself: 5N + 4H -1 = 9 electrons to go around. 4 bonds = 8 electrons 9 - 8 electrons = 1 electron left. So this 1 electron is placed on the central atom.