How to Write Chemical Formula?

A binary compound is composed of two different elements only. Formulae of binary compounds can be written with the help of valency of elements since both types of atoms forming the compound must lose, gain or share the same number of electrons.

Points to be considered to write the molecular formula

• Determine the valency of the elements present in the compound.
• Write the chemical formula such that the sums of the valency of the two elements are equal. Do this by determining the lowest common multiple of the two valency.
• Always place metals first in the formula.

Chemical Formula of Rust

Elements present in Rust are Iron and Oxygen. Then, 

Lowest common multiple of valency is 6. Therefore,

Fe = 2 × 3 = 6

O = 3 × 2 = 6

This implies that the chemical formula is Fe₂O₃

Chemical Formula of Aluminium Oxide

The elements present in Aluminium Oxide are Aluminium and Oxygen. Then, 

The lowest common multiple of valency is 6. Therefore,

Al = 2 × 3 = 6

O = 3 × 2 = 6

This implies that the chemical formula is Al₂O₃

Chemical Formula of Methane

Elements present in Methane are Carbon and Hydrogen. Then, 

Lowest common multiple of valency is 4. Therefore,

C = 1 × 4

H = 4 × 1

This implies that the chemical formula is CH₄

Chemical Formula of Sodium Chloride

Elements present in Sodium Chloride are Carbon and Hydrogen. Then, 

Lowest common multiple of valency is 4. Therefore,

Na = 1

Cl = 1

This implies that the chemical formula is CH₄

Chemical Formula of Calcium Oxide

Elements present in Calcium Oxide are Calcium and Oxygen. Then,

Lowest common multiple of valency is 2. Therefore.

Ca = 1 × 2

O = 1 × 2

This implies that the chemical formula is CaO.

Chemical formula is a way to describe chemical ratios of atoms that make up a specific chemical compound or molecule in chemistry. Chemical element symbols, numbers, and sometimes other symbols, such as parentheses, dashes, brackets, commas, plus (+), and minus (-) signs, are used to represent the chemical elements, atoms, or ions. A chemical substance that contains atoms from at least two different elements is referred to be a chemical compound. Chemical compounds and molecules both contain many atoms, but unlike chemical compounds, a molecule can just be made up of atoms from the same element.

In this article, we have covered, Definition of Chemical Formula, Importance of Chemical Formula, Types of Chemical Formulae, and others in detail.