Purdue University
Purdue University: Fundamental Subatomic Particles
At this site from the Purdue University, the elementary subatomic particles are described and electromagnetic radiation is detailed. Includes learning exercises and answers.
Encyclopedia Britannica
Encyclopedia Britannica: Hydrogen Ion
This brief entry describes the hydrogen ion, strictly, as the nucleus of a hydrogen atom separated from its accompanying electron. The hydrogen nucleus is made up of a particle carrying a unit positive electric charge, called a proton.
Sophia Learning
Sophia: Subatomic Particles: The Neutron: Lesson 2
This lesson will explain that neutrons are particles in the nucleus that have no charge and a mass of one amu. It is 2 of 3 in the series titled "Subatomic Particles: The Neutron."