More about ions

Elements may exist in compounds as ions. Ions are atoms or groups of atoms that bear an electrical charge due to having a different number of electrons than the number of protons.

Positive ions are known as cations and have fewer electrons than protons.
Na atoms have 11 protons and 11 electrons.
Na⁺ ions has 11 protons and 10 electrons.

Negative ions are known as anions and have more electrons than protons.
Cl atoms have 17 protons and 17 electrons.
Cl^– ions have 17 protons and 18 electrons.

Monatomic ions contain one atom. The type of ion formed by a particular element and the charge on that ion can be correlated with the position of the element in the periodic table.

1	2
Li⁺	Be²⁺		N^3–	O^2–	F^–
Na⁺	Mg²⁺	Al³⁺	P^3–	S^2–	Cl^–
K⁺	Ca²⁺				Br^–
Rb⁺	Sr²⁺				I^–
Cs⁺	Ba²⁺

Note that from the common ions above:
Metals form cations.

Noble Gases do not form any ions.

Most other nonmetals form anions.

Elements in the same group have monatomic ions with the same charge.