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

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.