# What elements must be bonded to hydrogen in order for hydrogen "bonding" to occur between the molecules?

Hydrogen bonding occurs where hydrogen is bound to STRONGLY electronegative elements, $\text{viz. nitrogen, oxygen, and fluorine.}$
You should also compare the boiling points of $N {H}_{3}$, $O {H}_{2}$, and $H F$, with the hydrides of the lower Group. i.e. $P {H}_{3} , S {H}_{2}$ etc. The normal boiling points of the first row hydrides, ARE VASTLY MORE ELEVATED then the hydrides of the lower Group atoms. And this difference can be attributed to the greater degree of hydrogen-bonding that operates in the hydrides of the MORE electronegative elements ($F , O , N$) of the first Period.