Covalent Bonding

Covalent bonding is the type of bonding that occurs between two non-metallic elements. Non-metallic elements do no form ions when they bond with each other. Instead, these element bond by the sharing of electrons. Sharing electrons allows them to obtain the noble gas structure (stable octet).

Each Chlorine shares its one unpaired electron with the other. The resulting molecule is more stable than the isolated atom from which it is formed. This compound is called chlorine gas.

Covalent compounds are also called molecules

The sharing of electrons is known as covalent bonding.

The covalent bond occurs because of he attraction of the positive nucleus of each atom to the pair of shared electrons (the electron of each atom is attracted to the protons of the other atom).

Covalent bonds form when atoms have 4 or more valence electrons with the exception of hydrogen.

Ex. Water is a covalently bonded compound

oxygen needs 2 electrons to completeits stable octet

Now both oxygen and hydrogen have stable electron configurations.

The unshared electron pairs are called lone pairs or unshared pairs or non-bonding pairs. They make no contribution to the bond between the atoms, but we will soon discover they do contribute to the molecular shape.

Multiple Bonds

Sometimes, the only way an atom can form a stable octet is through sharing two or more pairs of electrons. This sharing is known as a multiple bond.

Example: Oxygen gas

This kind of bond is known as a double bond. Both oxygen have eight electrons in their valence shell.

It is possible to have a triple bond, as shown below with nitrogen gas (N2), but there are no stable quadruple bonds

The compounds H2, N2, O2, F2, Cl2, Br2, and I2 are called diatomic molecules. You should know the formula for each of these compounds.

Structural Formula

Structural formulas are a simple way of drawing covalent compounds. Structural formulas are chemical formulas that show the arrangement of atoms in molecules and polyatomic ions. Only the bonds are represented.

Ex.

water

oxygen gas

nitrogen gas

Lewis Diagrams

All of the electrons of the elements involved in a covalent compound or polyatomic ion are accounted for in Lewis diagrams. The electrons indicate the way bonds connect the atoms in a molecule but they do not show the three dimensional molecular geometry of the molecule.

Ex. Carbon dioxide

Structural formulaDot diagram Lewis diagram

Ionic and Covalent Compounds

Covalent Compound Ionic Compounds

made up of molecules made up of repeating structural units

do not conduct electricity conduct electricity

usually liquids or gas at room temperature

usually solids at room temperature

low melting points high melting points

low boiling points high boiling points

usually two non-metals usually a metal and a non-metal

Naming covalent compounds...