What is an atom made of?

An atom has a tiny, dense centre called the nucleus, which contains protons (positively charged) and neutrons (no charge). Around the nucleus, electrons (negatively charged) move in regions called orbitals or shells.

The number of protons decides which element an atom is: hydrogen has one, carbon has six, oxygen has eight. Most of an atom is actually empty space. If the nucleus were the size of a cricket ball, the atom would be about the size of a stadium.