Rules to be followed to write the symbol of an element:

. If an element has a single English letter as a symbol, it should be written in the upper case.
H - Hydrogen
B - Boron
2. If an element has a two-letter symbol, the first letter should be written in the upper case and the second letter in the lower case.
Ca - Calcium
Ni - Nickle
Therefore, the symbol of an element signifies,
  • Name of the element.
  • One atom of the element.
The symbol "O" refers to the element of oxygen, i.e., one atom of oxygen.
Rules to be followed to write chemical formula:
1. The charges (\(+\), \(- \)) or valency (free electrons) on the ion must be balanced.
Ions must be balanced.
2. While writing a compound of metals and non-metal, the symbol of metal should be written first (left side) and followed  by the non-metal compound (right side).
\(NaCl\): Here, Sodium \(Na\) is a metal so that should be written on the left side, and chlorine \(Cl\) is a non-metal that should be written on the right side.
3. Ions should be enclosed in a bracket before writing the number to indicate the ratio.
So now, we will see how to write a chemical formula with some examples to understand it clearly in the next topic.