An atom is a tiny unit of a chemical substance. Everything is made up of atoms, including yourself. But what are atoms made of? Atoms are made up of Protons, Neutrons, and Electrons. Protons have positive energy, Electrons have negative energy, and Neutrons have Neutral energy. In an atom there is also something called the nucleus. The nucleus keeps the atom stable. The different amounts of Protons, Neutrons and Electrons in an atom are what decides what element they are. For example in copper there are 29 electrons, 29 protons, and 35 neutrons. Additionally, atoms are very small. If an atom was the size of a blueberry, and we wanted to see how many atoms there were in a grapefruit, then the grapefruit would have to be just as big as the Earth to fit all those blueberries.