Question

An atom of an element $A$ has three electrons in its outer shell and $B$ has six electrons in outermost shell. The formula of the compound formed between these two will be

• A. $A_6{B}_6$
• B. $A_2{B}_3$
• C. $A_3{B}_2$
• D. $A_{2}B$

Answer 1

Answer: (B)

In this case the valence electrons in the atom $A$ is three and hence its valency is generally $3$. In the atom $B$ the number of valence electrons is six. Hence its valency is usually $2$. Hence the formula of the molecule formed from $A$ and $B$ could be $A_2{B}_2$ . An example of two such elements are $Al$ and $O$ and the formula of Aluminium oxide is $A{l}_2{O}_3$.