How many electrons are in the outermost shell of alkali metals?

How many electrons are in the outermost shell of alkali metals?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (A)

Valence electrons drive the chemistry, and alkali metals are in Group 1, each with a single electron in their outermost shell. Their electron configurations end in s1, so the outer shell always contains just one electron, regardless of which alkali metal you consider (for example, Li is 1s2 2s1, Na is [Ne] 3s1, K is [Ar] 4s1). That lone valence electron is readily lost, giving a +1 charge, which explains their high reactivity. If the outer shell had two or three electrons, that would place the element in a different group, not among the alkali metals.

Valence electrons drive the chemistry, and alkali metals are in Group 1, each with a single electron in their outermost shell. Their electron configurations end in s1, so the outer shell always contains just one electron, regardless of which alkali metal you consider (for example, Li is 1s2 2s1, Na is [Ne] 3s1, K is [Ar] 4s1). That lone valence electron is readily lost, giving a +1 charge, which explains their high reactivity. If the outer shell had two or three electrons, that would place the element in a different group, not among the alkali metals.