Question

Explain the term variable valency. Why do some elements show variable valency? Give examples.
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Answer 1

Answer:

An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency. For example, iron combines with oxygen to form ferrous oxide as well as ferric oxide. ... This is termed variable valency.

Answer 2

Answer:

Certain elements combine with other atoms, donating, accepting or sharing electrons in different proportions depending on the nature of the reaction. For example, iron combines with oxygen to form ferrous oxide as well as ferric oxide. This is termed variable valency.