Isotopes and Ions

Isotopes are versions of a particular element that have different numbers of neutrons.

Ions are atoms (or molecules) that have lost or gained electrons and have an electrical charge.

Isotopes involve neutrons. Ions involve electrons.

Examples of Isotopes: O-16,   C-14,   H-1,  Cl-37

Examples of Ions: Na⁺,   Mg²⁺,   Cl^-,   O^2-

There is some overlap. For example, isotopes can lose or gain electrons to form ions. Isotopes of Chlorine (Cl) gain an electron when they form ionic bonds. This results in a negative ion (the Chloride ion).

The ionic charge is sometimes added to the nuclear notation at the top right of the element symbol.

When the charge on an atom is zero it means the number of protons is equal to the number of electrons. The atom is said to be neutral and there will not be a + or - written after the element symbol.

When an atom loses electrons it becomes a positive ion (called a cation). For example, when Lithium-7 (Li) loses an electron it becomes Li⁺. Only the number of electrons changes. It is now the Lithium-7 cation.

Exercise: Compete the table for the following atoms:

Formation of Isotopes and Ions

Isotopes can be made in supernovas, through radioactive decay of elements, and in specialized laboratories. The resulting isotopes have similar chemical and physical properties. In general it is difficult to make isotopes and involves a lot of energy. These are termed nuclear reactions.

Ions are made during many chemical reactions, when ionic compounds are dissolved in water, or when enough energy is applied to remove electrons. Ion formation is more common because electrons are on the outside of an atom and more easily added or removed. Much of chemistry deals with the behavior of electrons.