Hydrogen

Definition

Hydrogen is the first element on the periodic table with atomic number 1. It's also the lightest and most abundant element in the universe, making up about 75% of its elemental mass.

Related terms

Proton:

A subatomic particle found in the nucleus of every atom. The number of protons in an atom determines what element it is.

Electron:

A subatomic particle that carries a negative electric charge. It orbits around the nucleus of an atom.

Atomic Number:

This is defined as the number of protons found in the nucleus of an atom, which also defines its chemical properties.