5.2.1.4 Covalent bonding (small molecules)
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Covalent bonding occurs in most non-metallic elements and in compounds of non-metals.
For covalent bonding the particles are atoms which share pairs of electrons.
When atoms share pairs of electrons, they form covalent bonds.
These covalent bonds between atoms are strong.
Covalently bonded substances may consist of small molecules and giant covalent structures.
The covalent bonds in small molecules can be represented in the following forms:
For ammonia (NH3)
Forming hydrogen molecule (H2)
Hydrogen is group 1, so it has 1 electron on its outer shell.
To achieve a full stable outer shell of 2 electrons, hydrogen needs 1 more electron.
Each hydrogen atom shares 1 electron from its outer shell.
Forming fluorine molecule (F2)
Fluorine is in group 7, so it has 7 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, fluorine needs 1 more electron.
Each fluorine atom shares 1 electron from its outer shell.
The other 6 electrons from the outer shell are not shared.
Forming chlorine molecule (Cl2)
Chlorine is in group 7, so it has 7 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, chlorine needs 1 more electron.
Each chlorine atom shares 1 electron from its outer shell.
The other 6 electrons from the outer shell are not shared.
Forming bromine molecule (Br2)
Bromine is in group 7, so it has 7 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, bromine needs 1 more electron.
Each bromine atom shares 1 electron from its outer shell.
The other 6 electrons from the outer shell are not shared.
Forming oxygen molecule (O2)
Oxygen is in group 6, so it has 6 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, oxygen needs 2 more electrons.
Each oxygen atom shares 2 electrons from its outer shell.
The other 4 electrons from the outer shell are not shared.
Forming nitrogen molecule (N2)
Nitrogen is in group 5, so it has 5 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, nitrogen needs 3 more electrons.
Each nitrogen atom shares 3 electrons from its outer shell.
The other 2 electrons from the outer shell are not shared.
Forming Ammonia (NH3)
Nitrogen has 5 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, a nitrogen atom shares 3 electrons.
Hydrogen has 1 electrons on its outer shell.
To achieve a full stable outer shell of 2 electrons, each hydrogen atom shares 1 electron.
Forming Methane (CH4)
Carbon has 4 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, a carbon atom shares 4 electrons.
Hydrogen has 1 electrons on its outer shell.
To achieve a full stable outer shell of 2 electrons, each hydrogen atom shares 1 electron.
Forming Water (H2O)
Oxygen has 6 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, an oxygen atom shares 2 electrons.
Hydrogen has 1 electrons on its outer shell.
To achieve a full stable outer shell of 2 electrons, each hydrogen atom shares 1 electron.
Forming Carbon dioxide (CO2)
Carbon has 4 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, a carbon atom shares 4 electrons.
Oxygen has 6 electrons on its outer shell.
To achieve a full stable outer shell of 8 electrons, each oxygen atom shares 2 electrons.
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