atom![click to hear](/images/speaker.jpg)
Fundamental unit of matter having unique chemical properties; it is composed of a nucleus and an electron cloud. One atom is distinguished from another by the number of protons in its nucleus.
proton ![click to hear](/images/speaker.jpg)
Constituent particle of an atom’s nucleus whose electric charge is positive; it is composed of two u quarks and one d quark.
electron ![click to hear](/images/speaker.jpg)
Particle having a negative electric charge that moves around the nucleus of the atom.
nucleus ![click to hear](/images/speaker.jpg)
Central part of the atom whose electric charge is positive; it is composed of protons and neutrons, around which electrons revolve.
neutron ![click to hear](/images/speaker.jpg)
Constituent particle of an atom’s nucleus whose electric charge is neutral; it is composed of one u quark and two d quarks.