Atoms are made up of a nucleus, protons and electrons. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Atoms are the basic units of matter.

The difference lies in the structure of the atom's nucleus ... This stability seems partly connected to the mass of the atom, with heavier elements proving less stable. But in the 1940s and '50s, ...

The periodic table is one of the triumphs of science. Even before certain elements had been discovered, this chart could successfully predict their masses, densities, how they would link up with other ...