Key Concepts: Ions

Ions are charged particles that form when an atom gains or loses electrons.
A positive ion, also known as a cation, forms when an atom loses one or more electrons.
A negative ion, otherwise known as an anion, forms when an atom gains one or more electrons.
The charge of an ion is equal to the number of protons’ difference from the number of electrons. For example, if an atom has one more proton than electrons, it has a positive charge of +1.
Ions can be single atoms, like sodium ions (Na+), or they can be groups of atoms, like carbonate ions (CO3-2).
In ionic bonding, cations and anions come together to form compounds. This process is driven by the need for the atoms to reach a stable electron configuration.
Ionic compounds generally form between elements on the far left (metals) and far right (non-metals) of the periodic table.
An example of an ionic compound is sodium chloride (NaCl) where sodium (Na) loses an electron to become Na+ and chlorine (Cl) gains it to become Cl-. Together, they form an ionic bond.
Ionic compounds have high melting and boiling points due to the strong electrostatic forces between the positive and negative ions.
They also conduct electricity when molten or dissolved in water because their ions are free to move and carry charge.
Oxidation and reduction reactions (redox reactions) involve the transfer of electrons and are therefore associated with the formation of ions. In redox reactions, the substance that loses electrons is oxidised, and the substance that gains electrons is reduced.