Answer: It is one electron short of a noble-gas shell.
- A It is one electron short of a noble-gas shell
- B It forms strongly basic oxides on combustion
- C It has a very low ionisation enthalpy like them
- D It exists as a liquid at room temperature
Correct answer: A. It is one electron short of a noble-gas shell
Explanation: Like the halogens, hydrogen is one electron short of the nearest noble-gas configuration (He) and can gain an electron to form the hydride ion H<sup>-</sup>, so it is sometimes placed with Group 17.
Each water molecule's O-H bonds (covalent, solid) can hydrogen-bond (dashed) to neighbouring molecules, forming an extended network responsible for water's unusually high boiling point and density anomaly.
Concept context
The simplest and most abundant element in the universe. Study its unique position in the periodic table, isotopes (protium, deuterium, tritium), properties of water and hydrogen peroxide, and industrial uses.