Question

why do the hydrides of Oxygen and fluorine in group 16 and group 17 respectively show abnormally high melting point and boiling point as compared to other hydrides in their respective groups

Answer 1

Boiling points for hydrides depend mainly on Van der Waals forces between neighboring molecules and on electronegative polarity of the respective molecules themselves. The group 6A elements (Oxygen, Sulfur, Selenium, Tellurium) have two free electrons for bonding and form more strongly polar hydrides. This makes for stronger intermolecular attraction in the fluid, and thus higher boiling point. Water, exceptionally, is angular and strongly electronegative, therefore has the highest boiling point of all. The 7A elements (Fluorine, Chlorine, Bromine, Iodine) make weakly polar hydrides, and correspondingly weaker Van der Waals forces and intermolecular attraction; therefore their boiling points are lower.

Answer 2

Hello dear,

● Hydrides of O & F have exceptionally higher boiling points because -
- Oxygen and flourine are most electronegative elements in their respective groups.
- Thus O & F form stronger bonds with hydrogen in their hydrides.
- Intermolecular forces of attraction are stronger in water and hydrofluoric acid.
- Therefore, melting as well as boiling point of hydrides of O & F are exceptionally higher than corresponding elements in group.



Hope this helps you...