One of the smallest building blocks of matter is the atom. Atoms are made of a nucleus that contains protons and neutrons, and electrons that orbit the nucleus.

Atoms have a certain number of protons, neutrons and electrons. This is what makes one atom different from another.

Hydrogen, for example, has one proton and one electron. Helium has 2 protons and 2 electrons. Neon has 10 of each, while Aluminum has 13. . . Tungsten has 74 . . .