Bonding Case

Covalent Bonding

When atoms of two or more non-metals react together they form a chemical bond called covalent bonds. It occurs in a molecule when the electron in the highest energy level of each atom is shared. In covalent bonding no electrons are lost or gain.

Their atoms have share electrons to achieve the stable electron configuration of a noble gas Lewis and Evans (2006). Covalent substances can have either a giant covalent structure or a simple molecular structure. The forces of attraction between the molecules are small.

Giant covalent structures are huge 3 dimensional networks of atoms. Millions of atoms are all joined by strong covalent bonds. Simple molecular structures are made of small molecules, the atoms in each molecule are joined strong covalent bonds. No covalently bonded substances conduct electricity except for Graphite.

Properties of Covalent compunds

Low melting and boiling points, they are volatile - the molecules are not attracted towards each other by strong electrostatic forces, they are pulled apart @ relatively low temp.

Due to weak intermolecular forces, generally covalent compunds are liquids and gases at room temperature. However some covalent compounds are solids like iodine which is a black solid. Liquids: H2O, HCL, BR2. Gases: CO2, H2, CL2, NH3.

They are generally insoluble in water. They do not readily mix with water molecules because they do not contain ions. Compounds tend to dissolve readily in non-polar organic solvents such as benzene which also contains covalent molecules.

Single bond: Cl - Cl

Double bonds: CO2

Triple bonds: HCN

Rules

Hydrogen always forms one single bond.

Group 4: always end up with 4 bonds in total, could be 4 single, 2 double, 1 single and 1 triple.

Group 5: 3 bonds in total, 3 single, 1 single I double, 1 triple.

Group 6: 2 bonds in total, 2 single and 1 double.

Group 7: 1 bond.

e.g Methane CH Ethane C H

Ethanol C H OH Ethyne C H

Ethanoic Acid C H COOH

Shapes of Covalent bond molecule rules: electron pairs repel each other. They will be as far apart as possible.

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