Chem Terminology

Atom

The smallest unit of an element, made up of protons, neutrons, and electrons.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Neutron

A neutral subatomic particle found in the nucleus of an atom.

Electron

A negatively charged subatomic particle that orbits the nucleus.

Atomic Number

The number of protons in an atom, determines the element’s identity.

Atomic Mass

The total mass of an atom, roughly the sum of protons and neutrons.

Ion

An atom or molecule that has gained or lost electrons, resulting in a charge.

Cation

A positively charged ion (lost electrons).

Anion

A negatively charged ion (gained electrons).

Group (Column)

A vertical column on the periodic table; elements in the same group have the same number of valence electrons and similar chemical properties.

Period (Row)

A horizontal row on the periodic table; elements in the same period have the same number of electron shells.

Metals

Elements that are typically good conductors of heat and electricity, and are found on the left side of the periodic table.

Nonmetals

Elements that are poor conductors of heat and electricity, and are found on the right side of the periodic table.

Metalloids

Elements that have properties of both metals and nonmetals; found along the staircase on the periodic table.

Noble Gases

Group 18 elements, known for being chemically inert (non-reactive).

Ionic Bond

A bond formed between a metal and a nonmetal where electrons are transferred from one atom to another, resulting in the formation of ions.

Covalent Bond

A bond formed between two nonmetals where electrons are shared.

Polyatomic Ion

An ion made up of more than one atom, such as NO3− or SO42−.

Ionic Compounds

Formed between a metal and a nonmetal. The metal gives up electrons (forms a cation), and the nonmetal gains electrons (forms an anion).

Molecular (Covalent) Compounds

Formed between two nonmetals, where electrons are shared.

Roman Numerals

Used to indicate the charge of multivalent metals in ionic compounds.

Bohr-Rutherford Diagram

A representation of an atom, showing the nucleus (protons and neutrons) and the electron shells around it.

Electron Configuration

The arrangement of electrons in an atom’s shells.

Physical Change

A change that alters the appearance or state of a substance without changing its chemical composition.

Chemical Change

A change that results in the formation of new substances with different chemical properties.

Valence Electrons

The electrons in the outermost shell of an atom that are involved in chemical bonding.

Oxidation State (Charge)

The charge of an ion formed by an element; it indicates how many electrons an atom has gained or lost.