Question

Which of the following elements has only one valency?

• A. Phosphorous
• B. Iron
• C. Oxygen
• D. Nitrogen

Answer 1

The correct option is C

Oxygen

Explanation for correct option:

Valency is the combining tendency of an element or radical. It is the number of electrons lost or gained by an atom of an element in order to complete its octet and attain stability.

• Oxygen has only one valency i.e. 2

Explanation for incorrect option:

• Certain elements like iron ($\mathrm{Fe}$), copper ($\mathrm{Cu}$), Phosphorus ($\mathrm{P}$), etc. show more than one valency thus they possess variable valency.
• Iron has +2 and +3 valency, similarly copper has +1 and +2 valency. The suffix ous are used for the lower valency state and the suffix ic is for the higher valency state. For example, ${\mathrm{Fe}}^{2+}$is named ferrous and ${\mathrm{Fe}}^{3+}$is named ferric.

A) Phosphorous possess variable valency i.e. 3 and 5.

B) Iron also shows two valencies 2 and 3.

D) Nitrogen also shows variable valency i.e. 3 and 5.

Thus, option (C) Oxygen is the correct answer.