Abundance of the chemical elements

Our bodies, and everything else in the universe, is made up of tiny building blocks called chemical elements. There are lots of different kinds of chemical elements - like oxygen, carbon, and hydrogen - and there are lots of different amounts of each of them. This is called abundance: how much of a specific element is around in the universe. For example, there is lots of oxygen in our atmosphere, so oxygen is very abundant, but there is only a small amount of sodium in the universe, so sodium is less abundant. Each element is different - some are very abundant, some are not so much - but all the elements add up to make us and everything around us.