Question

Write down the formula of sodium sulphate using the criss cross method.

Answer 1

Hint: There is an old method to write the chemical formula of an ionic compound very easily and the method name is criss cross method. We have to follow a few steps to write the chemical formula of the compound by using the criss cross method.

Complete answer:
- In the question it is asked to write the chemical formula of the sodium sulphate by using the criss cross method.
- Few steps we have to follow to write the chemical formula of the sodium sulphate and they are as follows.
1) We have to identify the cation and anion of the chemical and have to write the cation symbol first and later anion method like as follows.
- In the chemical compound we know that sodium is cation and sulphate is anion.
\[\underset{Cation}{\mathop{\text{Na }}}\,\text{ }\underset{Anion}{\mathop{\text{S}{{\text{O}}_{\text{4}}}}}\,\]
2) We have to write the charge of each ion at their bottom like this:
\[\underset{1\text{ }}{\mathop{\underset{Cation}{\mathop{\text{Na }}}\,\text{ }}}\,\text{ }\underset{\text{2}}{\mathop{\text{ }\underset{Anion}{\mathop{\text{S}{{\text{O}}_{\text{4}}}}}\,}}\,\]
3) Now we have to apply the criss cross method like shown below.

- Means the number on the bottom of the element is going to multiple with the opposite element to get the chemical formula of the compound.
- Therefore the chemical formula of the sodium sulphate as per criss cross method is $N{{a}_{2}}S{{O}_{4}}$ .

Note:
By using criss cross method we can write chemical formulas of all the inorganic chemicals. This method criss cross method is not applicable to organic compounds because of the absence of the cations and anions in organic compounds.