We usually imagine atoms as being like tiny balls:
To make diagrams simpler we often draw atoms as circles:
There are over a hundred different types of atom, and these are calledelements. Each element has a special name. For example carbon, oxygen and hydrogen are all elements.
Lead and gold are elements too. A piece of pure gold contains only gold atoms. A piece of pure lead contains only lead atoms.
Chemical reactions join or split atoms to rearrange them. But they cannot change one element into another element, or anything simpler. A chemical reaction cannot turn lead into gold, becuse it can't change the atoms into different elements.
Each element is given its own chemical symbol, like O for oxygen and Cl for chlorine. Chemical symbols are usually one or two letters long, but sometimes three letters are used.
Every chemical symbol starts with a capital letter, with the second or third letters written in lower case.
For example, Mg is the correct symbol for magnesium, but mg, mG and MG are wrong.
Take care to write chemical symbols correctly
mg mG MG
Symbols and names
Sometimes it is easy to tell which element a symbol stands for. For example, Ostands for oxygen and Li stands for lithium.
But sometimes the symbol comes from a name for the element that is not an English word.For example, W stands for tungsten (from the word wolfram) andNa stands for sodium (from the word natrium).
The reason is that the same chemical symbols are used all over the world, no matter which language is spoken, which makes them most useful.