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Atoms are composed of protons, neutrons, and electrons (discovered in 1897). Protons and neutrons make most of the atom's mass and all of its positive charge in the nucleus.
Protons are subatomic particles that contain a positive charge. Essentially, they are hydrogen nuclei.
Neutrons are subatomic particles that have the same mass as a proton but not charge.
Electrons are subatomic particles with a negative charge that are found outside of the atom's nucleus.
An element's atomic number provides its location on the periodic table as well as describe how many protons are in an atoms of that particular element.
More than 200 subatomic particles have been detected so far, and most appear to have a corresponding antiparticle.
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