Question

The hydrides of the first element in group 15-17, namely $N{H}_3,H_{2}O$ and $HF$, respectively show abnormally high values for melting and boiling points. This is due to:

• A. small size of $N,O$ and $F$
• B. the ability to form extensive intermolecular $H$-bonding
• C. the ability to form extensive intramolecular $H$-bonding
• D. effective van der Waal's interaction

Answer 1

The correct option is B the ability to form extensive intermolecular $H$-bonding

The reason is due to the ability to form extensive intermolecular H-bonding because of the small size and high electronegativity of elements, have the ability to form extensive intermolecular (i.e., between two molecules) hydrogen bonding.

Thus, a large amount of energy is required to break these bonds, i.e., the melting and boiling points of hydrides of these elements are abnormally high.

Hence, option B is correct.