Chapter 7, Problem 122A

Interpretation Introduction

Interpretation:

The oxidation number of each of the ions found in the compound ${\text{BeAl}}_{\text{2}}{\text{O}}_{\text{4}}$ needs to be determined and the formation of the ionic compound needs to be explained.

Concept introduction:

Oxidation number, also named as Oxidation State is the number of electrons which an atom either loses or gains to form chemical bonds with another atom.

Answer to Problem 122A

The oxidation states of Berrylium, oxygen, aluminium are +2, -2 and +3 respectively.

Explanation of Solution

The oxidation state of group 2 elements is +2, that is, they form +2 cations, such as Berrylium, magnesium etc. The group 16 elements, such as, oxygen, phosphorus etc forms -2 anions. To form the neutral compound, ${\text{BeAl}}_{\text{2}}{\text{O}}_{\text{4}}$, the oxidation state of aluminium can be calculated.

Take the oxidation state of aluminium x, add the oxidation sate of all atoms in the compound and equals to zero as the compound is a neutral compound.

$\begin{array}{c}{\text{BeAl}}_{\text{2}}{\text{O}}_{\text{4}}\\ 2+2x-8=0\\ 2x=6\\ x=\frac{6}{2}\\ =3\end{array}$

So, the oxidation state of aluminium is +3.

Conclusion

The overall charge of a neutral compound is 0.