Chapter 28, Problem 21Q

To determine

Why noble gases are nonreactive whereas alkali metals are highly reactive.

Answer to Problem 21Q

Solution:

Noble gases cannot lose or gain outermost electron, hence are nonreactive.

Alkali metals can easily give away outermost electron, hence are very reactive.

Explanation of Solution

How reactive a thing is depending on how easily it can lose or gain electrons in its outermost shell. Noble gases have fully filled outer shells and hence cannot accommodate a new electron or lose an electron. Hence, they are unable to react.

Alkali metals have a loosely bound single electron in the outermost shell which they can give away easily to react with other things. Hence alkali metals are highly reactive.