Chapter 18, Problem 5STP

To determine

The oxidation number of sodium in the compound ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ .

Answer to Problem 5STP

The correct option is (D).

Explanation of Solution

Given:

The compound is ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ .

Calculation:

The oxidation number of an element is generally equal to the group number. Sometimes it is equal to the number of electrons lost or gained in order to complete its outermost shell and attain the noble gas configuration and get stabilized.

Sodium belongs to group 1 and its oxidation number is 1+. As ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ has 3 sodium atoms, therefore oxidation state of sodium in ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ is 3+.

Phosphate has overall 3- charge and compound ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ is overall a neutral compound.

Thus, ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ is a neutral compound and the sodium atom will have an oxidation number of 3+.

Conclusion:

Hence, the oxidation number of sodium in the compound ${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$ is +3.