Question

What do you understand about the term variable valency? give the example.

Answer 1

Explanation:

Valency:

• Is the combining capacity of an element.
• The number of electrons donated or accepted by an atom of an element so as to have the electronic configuration of the nearest noble gas is called its valency.

Variable valency:

• Sometimes, because of different conditions under which a chemical reaction takes place, the valency of the same element changes. Thus metals like lead, tin, copper, mercury, iron, etc exhibit variable valency.
• Normally, the metals donate electrons from their valence shell, so as to form positively charged ions.
• However, some metals lose electrons from the shell next to the valence shell. In such a situation the element exhibits more than one electropositive valency. Such elements are said to have variable valency.

Example

• Iron (Fe), May have a valence of both 2 and 3.