science final words

atom

the smallest particle of an element that retains all the properties of that element

atomic number

the number of protons(electrons) in an atom.

isotopes

atoms of the same element with different numbers of neutrons.

mass number

the number after an element's name, representing the sum of its protons and neutrons.

atomic mass unit

one-twelfth the mass of a carbon-12 atom.

atomic mass

the weighted average mass of the isotopes of that element.