While writing the symbols of elements you have to follow these rules-
1.The first letter of a symbol is always written in capital. For example - H(symbol of hydrogen).
2.The second letter of a symbol is always written in small. For example- Fe(symbol of iron).
3.Some elements also have their Latin names, so their symbols are derived from the Latin name
element. Latin symbol
For example- Gold- Aurum (Au)
Silver Argentum (Ag)
I hope it helps:)