IB Physics E.1 Structure of the Atom Key Definitions

Absorption spectrum is the range of frequencies of electromagnetic radiation readily absorbed by a substance by virtue of its chemical composition.

The distance of closest approach is the minimum distance an alpha particle can reach during a head-on collision with a nucleus. This distance is determined using energy conservation.

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule transitioning from a high energy state to a lower energy state.

A photon is a tiny particle that comprises waves of electromagnetic radiation.

The strong nuclear force is one of the four fundamental forces of nature and is responsible for holding the nucleus together. It acts between all nucleons (protons and neutrons).