Unit 4A: Atoms

atom

the smallest particle of an element that still retains the properties of a larger sample of the element

subatomic particle

any particle that is smaller than an atom

charge

a fundamental property of matter that can be either positive or negative

atomic number

the number of protons in atoms of an element

nucleus

the center of an atom

electromagnetic force

an attractive or repulsive force of nature that exists between electric charges

strong force

an attractive force of nature that exists between protons and neutrons

energy level

a region of the electron cloud within which certain electrons can be found

valence shell

the furthest energy level from the nucleus

valence electron

an electron in the outermost energy level of an atom

isotopes

two or more atoms of the same element that have different numbers of neutrons

mass number

the sum of the protons and neutrons in an atom

atomic mass

the combined mass of the protons, neutrons, and electrons in an atom

average atomic mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element