What do atoms make up?

The smallest unit of an element, consisting of at least one proton and (for all elements except hydrogen) one or more neutrons in a dense central nucleus, surrounded by one or more shells of electrons. In electrically neutral atoms, the number of protons equals the number of electrons. read more

A: Atoms are made of protons, neutrons and electrons with the exception of hydrogen atoms, which do not have any neutrons. The nucleus of an atom contains the protons and neutrons, and the electrons are found outside the nucleus in orbitals. read more

All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to 1.07 3 √ A fm, where A is the total number of nucleons. read more