What is the main reason why hydrogen can have a variable valency?
- A It has only one electron in its outer shell.
- B It has a high electronegativity.
- C It is a metal.
- D It is a noble gas.
The main reason hydrogen can have a variable valency is that it has only one electron in its outermost shell (1s orbital). This single electron allows hydrogen to either lose or gain an electron during chemical reactions, depending on the electronegativity of the atom it is interacting with. When hydrogen reacts with a more electronegative element, such as oxygen or nitrogen, it tends to lose its electron, resulting in a positive valency (H+). In contrast, when hydrogen reacts with an electropositive element, such as an alkali metal, it can gain an electron to form a hydride ion (H-), resulting in a negative valency. This flexibility in losing or gaining an electron, made possible by the single electron in its outer shell, enables hydrogen to have a variable valency and participate in a wide range of chemical reactions and compounds.
