Unit 5: Atomic Structure

IPC

ATOM

The smallest particle on an element that still has the properties of that element.

PROTON (p⁺)

Positive particle in the nucleus of an atom.

NEUTRON (n⁰)

Neutral particle in the nucleus of an atom.

ELECTRON (e⁻)

Negative particle outside of the nucleus in the electron cloud.

QUARKS

Smaller particles that make up protons and neutrons.

VALENCE ELECTRON

An electron that is found in the outermost shell of an atom and therefore determines the atom's chemical properties.

ATOMIC NUMBER

The number of protons in the nucleus of an atom. Used to identify an element. Periodic table is arranged in increasing order of this number.

MASS NUMBER

The number of protons and neutrons in the nucleus of an atom.

ISOTOPES

Atoms of the same element with different numbers of neutrons.

AVERAGE ATOMIC MASS

Weighted average of all of the different versions of an element (called isotopes).

GROUPS

The vertical columns on the periodic table. All elements in the same group have the same number of valence electrons and therefore share similar characteristics.

PERIODS

The horizontal rows on the periodic table. All elements in the same period have the same number of energy levels in their electron cloud.