Question

What is a chemical formula? What is the rule for writing a formula correctly?

Answer 1

Hint:To define the chemical composition of the compound we used to define its chemical formula. The symbols of elements are included in the formula along with the ratio in which they are present.

Complete answer:
A chemical formula is a representation of the elements that are present within a compound along with the definite proportion of these elements. For example the chemical formula for carbon dioxide is \[{\text{C}}{{\text{O}}_2}\] . Looking at the chemical formula we get an idea that in one molecule of carbon dioxide contains one atom of carbon and 2 atoms of oxygen. Knowledge of chemical formula of any compound is very important for us because:
A chemical formula gives the elements present along with the ratio present. We can also get a slight idea about the type of species such as ionic, neutral or radical is present in the compound.
The rules for writing the chemical formula are:
-While writing the chemical formula an anion is always written on the right side and the cation is always written on the left.
-In case of metal and non metal, the symbol of non metal is always written first and then the symbol of non metal.
-The valency of the elements must be balanced.

Note:
We can represent the chemical formula in two ways as a molecular formula and as an empirical formula. Molecular formula tells us the exact number of atoms present in a compound whereas the empirical formula only represents the ratio in which the elements are present. For example the molecular formula of glucose is \[{{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6}\] where as the empirical formula is \[{\text{C}}{{\text{H}}_2}{\text{O}}\] .