Question

Elements of group 1 and elements of group 17 both have valency 1. Explain.

Answer 1

Group 1 elements contain a single electron in their valence shell, which they lose to acquire stability. As a result, they have a valency of 1⁺. Elements in group 17 have 7 electrons in their valence shell but lack one electron to make an octet. They gain one electron and have a 1⁻ valency.

\[\ce{\underset{(2, 8, 1)}{Na}- e- -> \underset{(2, 8)}{Na+}}\]

\[\ce{\underset{(2, 8, 7)}{Cl}+ e- -> \underset{(2, 8, 8)}{Cl-}}\]

Hence, elements of group 1 and elements of group 17 both have valency 1.