What does the subscript indicate in the chemical formula \[{\text{C}}{{\text{O}}_2}\]?

Hint: We should have a basic knowledge of chemical names and the chemical formulas of the compounds. We need to remember that the chemical name of the compound \[{\text{C}}{{\text{O}}_2}\] is carbon dioxide.

 Complete answer:
We need to remember that the subscript in the given formula denotes the number of atoms present in it.
As we know that in the given formula of \[{\text{C}}{{\text{O}}_2}\], the subscript \[2\]indicates that , there are two atoms of oxygen present in the molecules of carbon dioxide. Carbon dioxide is a compound which is formed by the combination of two different atoms i.e. carbon and oxygen.
It’s chemical name is carbon dioxide, it also suggests that there are two atoms of oxygen used.
Hence, the subscript \[2\] in carbon dioxide that is \[{\text{C}}{{\text{O}}_2}\] denotes atoms of oxygen.

Additional information:
We need to know that carbon dioxide is one of the reactants used in the process of photosynthesis. Carbon dioxide is one of the components of air. Its composition in air is around \[0.04\% \]. Carbon dioxide is a covalent compound formed by the sharing of electrons between the two atoms. Covalent compounds generally have Vander wall forces of attraction.
The symbol of Carbon is \[{\text{C}}\]. Its atomic number is \[6\] and mass number is \[12\].
The symbol of oxygen is \[{\text{O}}\]. Its atomic number is \[8\] and mass number is \[16\].
Oxygen family is also known as chalcogens.

Note:
Students might make a mistake with the number of molecules and number of atoms. Number of molecules are always written as coefficients whereas the number of atoms are always written as subscripts.