The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and one electron in the region outside the nucleus. The electron and proton are attracted to each other.

Quarks are the reason protons have a positive charge. Each quark has a fraction of an electric charge. A proton has two up ...

Key fact: isotopes are forms of an element that have the same number of protons but different numbers of neutrons. There are three isotopes of hydrogen: hydrogen, deuterium (hydrogen-2 ...