Atom
a tiny particle that is the fundamental building block of all substances and whose properties determine the properties of an element made up only of those atoms.
Atomic Mass
the measure of the mass of an atom, generally the sum of the protons and neutrons; this term is used when referring to a single atom or atoms of a single isotope.
Atomic Nucleus
the positively charged core of an atom, which is composed of positively charged protons and electrically neutral neutrons.
Atomic Number
the number of protons in every atom of an element.
Electron
a tiny part of an atom with a negative electrical charge.
Proton
a positively charged particle found in the nuclei of atoms.
Neutron
a neutral particle with approximately the same mass as a proton, found in nuclei of atoms along with protons.
Isotope
atoms of the same element that differ in the number of neutrons in the nucleus,