Chemistry

A covalent bond is formed between non-metal atoms, which combine together by sharing electrons. Water and carbon dioxide exist as simple molecules.

There are different types of bonding, including:

• Ionic bonding between metals and non-metals
• Covalent bonding between non-metals

A covalent bond is a shared pair of electrons, shared between two non-metal atoms.

Simple molecules

Simple molecules consist of a small number of atoms joined by covalent bonds. For example, water and carbon dioxide exist as simple molecules. The covalent bonds joining the atoms together in a simple molecule are strong. However, the intermolecular forces between simple molecules are weak.

Columns in the table - groups

The elements in any one vertical column are said to be in the same group or family.

Eight of the groups are numbered from left to right. Elements in the same group have similar chemical properties.

The group number is the same as the number of electrons in the outer shell of all the elements in the group.

Rows in the table - Periods

Elements in the same horizontal row are said to be in the same period. The periods are numbered from top to bottom.

The period number is the same as the number of electron shells that are occupied.