Question

The valency of zinc is 2 and the valency of oxygen is also 2. Construct the formula for zinc oxide by using these hints.

Answer 1

- Hint: The valency determines the combining capacity of an element to form a compound. If any two elements have the same valency, then one atom of each element will combine forming the compound.

Complete step-by-step solution -

The valency of zinc is two and also the valency of oxygen is two. Using these two hints we have to form the formula of the compound zinc oxide. Let us see in a step by step manner.
Valency is the combining capacity of an element with other elements to form a compound.
For the formation of an ionic compound, the two elements which will combine to form the ionic compound will either lose or gain the same number of electrons as their valency. The electropositive element will lose electrons while the electronegative element will gain electrons.
In the case of a covalent bond, the elements share the same number of electrons as their valency. For example, if the valency of an element is 3, it will share 3 electrons either with a single element also having valency 3 or with three different elements having valency 1.
Zinc has a valency of 2. Zinc is a metal and it is electropositive. That means it will readily lose electrons. Since the valency of zinc is 2, it will lose 2 electrons. On the other hand, oxygen has a valency of 2 but it is non-metal and it is highly electronegative. So, it will gain 2 electrons due to its valency.
Now, we know that zinc and oxygen combine to form zinc oxide. So, zinc will lose two electrons and the same electron will be accepted by oxygen to form zinc oxide. Therefore, one atom of zinc and one atom of oxygen combines to form zinc oxide.
So, the formula of zinc oxide will be ZnO. See the illustration below for better understanding.
Valency 2 2
Elements Zn O
Formula ${ Zn }_{ 2 }{ O }_{ 2 }$
Cancelling out the common factor 2, we get the formula of zinc oxide ZnO.

Note: Don’t confuse valency with oxidation state. Valency is the number of electrons an element can lose or gain to form a compound while the oxidation state is the number of electrons an element has gained or lost after the formation of a particular compound.