Atoms and Elements

Atomic Mass

average mass of all of the protons and neutrons in an atom

atomic number

number of protons in an atom's nucleus

chemical symbol

an abbreviation below the atomic number containing one or two letters

atoms

Building blocks of matter made up of protons, neutrons, and electrons

element

A pure substance made of only one kind of atom

proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom

neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom

electron

A subatomic particle that has a negative charge

nucleus

The center of an atom, containing the protons and neutrons

strong force

holds the nucleus together

atomic number

the number of protons in the nucleus of an atom

atomic mass

Number of protons and neutrons

shells

Energy levels where the electrons are found

valence electrons

electrons in the outermost shell