An electron is heavier than a proton.
The electrons comprise most of the atomic volume and thus are the parts that "intermingle" when atoms combine to form molecules.
Isotopes are atoms with the same number of neutrons different numbers of protons.
40Ca2+ has a mass number of 40 and a net charge of 2+.
40Ca2+ contains 20 protons and 18 electrons.
The mass of a neutron is approximately the same as the mass of a proton.
31P contains 15 neutrons and has a net charge of 1+.
The nucleus contains protons, neutrons, and electrons.
The proton has a positive charge equal in magnitude to the electron's negative charge.
Rutherford created the cathode-ray tube and was the founder of the charge-to-mass ratio of an electron.
J.J. Thomson experimented with alpha particles striking thin metal foils which led him to postulate the nuclear atom.
In nature, most elements are mixtures of isotopes.