Chem

Ion

An atom or group of atoms that has a charge (+ or -).

Charge

Atoms develop a charge when electrons are lost or gained; present in ionic substances.

Oxidation number

The number assigned to an atom based on the sharing of electrons; in ionic substances, charge equals oxidation number.

Monatomic ion

An ion made from a single atom (e.g., Na+, sodium ion).

Polyatomic ion

An ion made from more than one atom (e.g., NO3-, nitrate ion).

Monovalent

Describes an ion having only one possible charge (oxidation #).

Monovalent ions

Ions that can have charges of 1+, 2+, 3+, 3-, 2-, 1-, or 0.

Calcium ion

Ca2+ has a 2+ charge.

Fluoride ion

F- (from fluorine) has a 1- charge.

Exception for hydrogen

Hydrogen can also form a 1- ion (H-), called the hydride ion.

Silver ion

Ag+ is a monovalent ion not in the standard columns.

Zinc ion

Zn2+ is a monovalent ion not in the standard columns.

Cadmium ion

Cd2+ is a monovalent ion not in the standard columns.

Periodic Table groups

Elements in specific groups take on the charge indicated above the column when they become ions.