Question

Element A has 3 electrons in the outermost orbit and Element B has 6 electrons in the outermost orbit. The formula of the compound would be:
A.${{\text{A}}_{\text{2}}}{{\text{B}}_{\text{3}}}$
B.${{\text{A}}_{\text{2}}}{{\text{B}}_{\text{6}}}$
C.${{\text{A}}_{\text{2}}}{\text{B}}$
D.${{\text{A}}_3}{{\text{B}}_2}$

Answer 1

The chemical formula of a compound is an expression that shows the elements present in the compound and the relative proportions of the elements present in the compound. The valency of the elements are cross multiplied to get the formula.

Complete answer:
The chemical formula of a compound is the representation of the ratio of the elements present in the compound. For example, the chemical formula of water is ${{\text{H}}_{\text{2}}}{\text{O}}$ means that the hydrogen and oxygen are present in it in the ratio of (2:1).
According to the question, it is given that Element A has 3 electrons in the outermost orbit and Element B has 6 electrons in the outermost orbit. The element with three electrons in the valence shell should belong to group 13 (IIIA) and that with six electrons should belong to group 16 or (VIA). A general formula of this compound should be ${{\text{A}}_{\text{2}}}{{\text{B}}_{\text{3}}}$ just like the chemical formula of aluminium oxide is ${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}$. This is because the valency of element A is 3 and that of element B should be 2.
So, the correct answer is option A.
Note:
The molecular formula of a compound is a chemical formula of the molecular compound that shows the kinds and the numbers of the atoms present in the molecule of a compound. An empirical formula is the formula that shows the elements in a compound in their lowest whole number ratio. For example, the molecular formula of glucose is ${{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}$ while the empirical formula of the for compounds such as water, the molecular formula is the same as the empirical formula.