Question

An element X which occurs in the second period has an outer electronic structure ${{\text{s}}^2}{{\text{p}}^2}$ . The formula and acid-base character of its oxide, respectively are,
A.${\text{X}}{{\text{O}}_3}$ , basic
B.${{\text{X}}_2}{{\text{O}}_2}$ , basic
C.${{\text{X}}_2}{{\text{O}}_3}$ , amphoteric
D.${\text{X}}{{\text{O}}_2}$ , acidic

Answer 1

To solve this question, it is required to have knowledge about oxide formation of p-block elements as well as the nature of the oxide formed. P-block elements mostly form acidic or amphoteric oxides. The formula of the oxide formed will depend upon the valency of the element, i.e. its ability to lose electrons.

Complete step by step answer:
The formula of the oxide formed will depend on how many electrons the element can lose. Oxygen being electronegative will add two extra electrons in its valence shell and will assume $- 2$ oxidation state in its oxides. In the question, as it is given that the element is present in the second period, this means that it does not have a d-orbital. The electronic structure of the element is ${{\text{s}}^2}{{\text{p}}^2}$ . So, during oxide formation, it will lose four electrons in its valence shell and shall acquire $+ 4$ oxidation state. So, when it will combine with oxygen in its $- 2$ oxidation state to form an electrically neutral compound, one atom of the element will be able to combine with two oxygen atoms. Thus, the formula of the compound shall be ${\text{X}}{{\text{O}}_2}$ . As we know, the element X will have a vacant p-orbital orbital and can thus act as a Lewis acid. So, the character of the oxide will be acidic.

$\therefore$ The correct option is option D, i.e. ${\text{X}}{{\text{O}}_2}$ and acidic.

Note:
In this question, we could also first identify the element and then identify the acid it forms. In this case, the element is in the second period, so n will be two. Thus, its electronic configuration will be ${\text{1}}{{\text{s}}^2}{\text{2}}{{\text{s}}^2}{\text{2}}{{\text{p}}^2}$ which is the electronic configuration of carbon. So, the element X is carbon and the oxide it forms is ${\text{C}}{{\text{O}}_2}$ which is an acidic oxide as it forms carbamic acid in water.