Write the complete electron configuration of the group 2a element in the fourth period. (your answer should be of the form: 1s^? +2s^? +2p^? +3s^? . . )

Ca₂₀ = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Explanation:

The element of group 2A in 4th period is calcium.

Its atomic number is 20.

Its atomic weight is 40.08 amu.

It is third most abundant metal.

It is silvery soft metal.

It react rapidly with water and air.

It is also used as reducing agent.

it is used to make the alloy with copper, aluminium and beryllium.

Its electronic configuration is:

Ca₂₀ = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

1s² 2s² 2p⁶ 3s² 3p⁶ are inner electrons.

4s² are valance electrons. Thus it loses two valance electrons to get complete octet.

Abbreviated electronic configuration:

Ca₂₀ = [Ar] 4s²