Ions are formed when atoms gain or lose electrons to form full outer shell.
Metals: lose electrons and form positively charged ions
Non-metals: gain electrons and form negatively charged ions
For example, a magnesium atom loses the two outer electrons and becomes a magnesium ion.
Similarly, an oxygen atom gains two electrons and becomes an oxide ion.
These are the ionic charges of common ions that you should know 👇
Ionic Compounds and Ionic Bonds
Ionic compounds are formed when a metal transfers electrons to a non-metal.
Ionic bonds from between positively charged ions and negatively charged ions due to electrostatic attraction between opposite charges.
Example 1. Formation of magnesium oxide (MgO)
- Magnesium transfers two outer electrons to oxygen.
- Mg2+ ion and O2- ion are formed.
- The electrostatic attraction between Mg2+ ion and O2- ion forms the ionic bond between magnesium and oxygen.
- The chemical formula for the ionic compound is MgO.
Example 2. Formation of magnesium chloride (MgCl2)
- Magnesium transfers one electron each to two chlorine atoms.
- One Mg2+ ion and two Cl- ions are formed.
- The electrostatic attraction between Mg2+ ion and Cl- ion forms the ionic bond between magnesium and chlorine.
- The chemical formula for the ionic compound is MgCl2.
Ions in an ionic compound are arranged in a regularly repeating pattern called the ionic lattice.
Ionic lattices are formed because there is a strong electrostatic force acting between ions.
👆 This is an example of a 3D ionic lattice formed by sodium chloride (NaCl).
Properties of Ionic Compounds
I. High Melting and Boiling Points
- For a substance to melt or boil, energy is needed to break the bonds between particles.
- Ionic compounds are held together by many strong electrostatic forces, therefore need a large amount of energy to break the ionic bonds.
- Ionic compounds have high melting and boiling points, and they are usually solid in room temperature.
II. Electricity Conduction
- If ionic compounds are molten or in aqueous state, electrically charged particles are free to move around. Therefore, they can conduct electricity.
- In solid state, ions are fixed in the lattice, so electricity cannot be conducted.