When most of us picture an atom, we think about a small nucleus made of protons and neutrons orbited by one or more electrons. We view these electrons as point-like while rapidly orbiting the nucleus.

Protons are tiny particles just a femtometer across, but without them, atoms wouldn't exist. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.

The Bohr model, introduced by Danish physicist Niels Bohr in 1913, was a key step on the journey to understand atoms. Ancient Greek thinkers already believed that matter was composed of tiny basic ...