Everything is made from atoms, and there are over 100 different types. These are called elements, and they can be divided into the metals and the non-metals. We'll look at their physical and chemical properties in this Revision Bite.
Everything is made from atoms, including you. Atoms are tiny particles that are far too small to see, even with a microscope. If people were the same size as atoms, the entire population of the world would fit into a box about a thousandth of a millimetre across!
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 called elements. 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
Symbols and names
Sometimes it is easy to tell which element a symbol stands for. For example, O stands 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) and Na 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.
The periodic table
All the different elements are arranged in a chart called the periodic table.
The horizontal rows are called periods.
The vertical columns are called groups.
Elements in the same group are similar to each other.
The metals are on the left and the non-metals are on the right.
One non-metal, hydrogen, is often put in the middle.
The main groups are numbered from 1 to 7 going from left to right, and the…