# Are hydrogen bonds formed between all molecules?

Jul 20, 2017

Well no.........

#### Explanation:

Hydrogen bonding is an INTERMOLECULAR phenomenon, i.e. it occurs betweens molecules which possess an hydrogen atom that is bound (directly, or occasionally, indirectly) to a strongly electronegative element such as $F , O , N$.

Because the heteroatoms are more electronegative than hydrogen, they strongly polarize electron density towards themselves.

The result? A molecular dipole, that which we could represent as $\stackrel{\delta +}{H} - \stackrel{\delta -}{F}$ or $\stackrel{\delta +}{H} - \stackrel{\delta -}{N} {H}_{2}$ or $\stackrel{\delta +}{H} - \stackrel{\delta -}{O} - \stackrel{\delta +}{H}$. AS the gas or the liquid these dipoles tend to align, viz.

${\stackrel{\delta +}{H}}_{2} \stackrel{\delta -}{O} \cdots \stackrel{\delta +}{H} - \stackrel{\delta -}{O} - \stackrel{\delta +}{H} \cdots O {H}_{2} \cdots$

This is an INTERMOLECULAR force that substantially DECREASES the volatility of hydrogen bound species.

And if you interrogate the normal boiling points of these materials, they are SUBSTANTIALLY increased with respect to the lower group analogues, i.e. $P {H}_{3}$, ${H}_{2} S$, $H C l$. Anyway please look at the data in your text.