Chemical Bonds: Covalent, Ionic, and Metallic Explained

Posted on Jan 9, 2025 in Chemistry

Unit 5: Chemical Bonding

1. Introduction

The things around us are made up of different atoms that have been joined together.

1.1. What Happens When Atoms Bond?

A chemical bond is formed when atoms are held together by attractive forces. A chemical bond is the physical process that causes atoms and molecules to be attracted to each other and held together in more stable chemical compounds. There are three types of chemical bonds: covalent, ionic, and metallic bonding.

1.2. Lewis Structures

Lewis notation uses dots and crosses to represent the valence electrons on different atoms.

2. Covalent Bonding (Non-Metals)

Covalent bonding occurs between the atoms of non-metals. The shared electrons move in the orbits around both atoms. As they move, there is an attraction between the negatively charged electrons and the positively charged nuclei.

Covalent bonding is a form of chemical bonding where pairs of electrons are shared between atoms.

• In a single covalent bond, two electrons are shared between the same two atoms, one electron from each atom.
• In a double covalent bond, two electrons from each atom are shared.
• In a triple covalent bond, three electrons from each atom are shared.

Valency is the number of electrons in the outer shell of an atom which are able to be used to form bonds with other atoms.

2.2. Properties of Covalent Compounds

1. The melting and boiling points of covalent compounds are generally lower than those of ionic compounds.
2. The molecules in covalent compounds are able to move around to some extent and can sometimes slide over each other.
3. Covalent compounds generally aren’t very soluble in water.
4. Covalent compounds generally don’t conduct electricity when dissolved in water.

2.3. Covalent Crystals

Atoms in covalent solids are covalently bonded with their neighbors, creating, in effect, one giant molecule.

3. Ionic Bonding

When electrons are transferred from one atom to another, it is called ionic bonding.

Ionic bonding is a type of chemical bond where one or more electrons are transferred from one atom to another.

3.2. The Crystal Lattice Structure of Ionic Compounds

Ionic substances are actually a combination of lots of ions bonded together into a giant molecule. The arrangement of ions in a regular, geometric structure is called a crystal lattice.

3.3. Properties of Ionic Compounds

1. Ions are arranged in a lattice structure.
2. Ionic solids are solid at room temperature.
3. The ionic bond is a strong electrostatic attraction. This means that ionic compounds are often hard and have high melting and boiling points.
4. Ionic compounds are brittle, and bonds are broken along planes when the compound is put under pressure.
5. Solid crystals don’t conduct electricity, but ionic solutions do.

4. Metallic Bonding (Metals)

In a metallic bond, the valence electrons are delocalized, meaning that an atom’s electrons don’t stay around that one nucleus.

Metallic bonding is the electrostatic attraction between the positively charged atomic nuclei of metal atoms and the delocalized electrons in the metal.

4.2. Properties of Metals

1. Metals are shiny.
2. Metals conduct electricity because electrons are free to move.
3. Metals conduct heat because the positive nuclei are packed closely together and can easily transfer the heat.
4. Solid metals are crystalline; the particles are close together and in a regular arrangement.