Question

The formula of the compound is ${\mathrm{A}}_2{\mathrm{B}}_5$. The number of electrons in the outermost orbits of A and B respectively are?

Answer 1

Step1. Calculation of valency of A and B atom

• The formula of the compound is ${\mathrm{A}}_2{\mathrm{B}}_5$.
• It can be written as ${\mathrm{A}}^{+5}{\mathrm{B}}^{-2}$.
• So, the valency of atom A is five, and B is two.

Step2. Number of electrons in outermost orbitals of A

• The valency of atom A is five. So, the number of electrons in the outermost orbits of A is five.

Step3. Number of electrons in outermost orbitals of B

Number of electrons in outermost orbitals of B = $8-\text{Valency}$

=$8-2=6$

So, the number of electrons in the outermost orbits of A and B respectively are $5$, and $6$.