Covalent Bonding

Covalent Bonding

• Covalent bonding occurs between non-metal elements. It involves the sharing of electron pairs between atoms, to achieve stability and a full outer shell.
• These electron pairs are commonly known as shared pairs or bonding pairs, and the stable balance of attractive and repelling forces between atoms results in a covalent bond.
• Covalent bonds form molecules. Hence, a molecule is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound.

Single, Double, and Triple Covalent Bonds

• Covalent bonds can be single, double, or triple bonds, depending on the number of shared electron pairs.
• A single covalent bond shares one pair of electrons (two electrons), a double bond shares two pairs (four electrons), and a triple bond shares three pairs (six electrons).
• For example, a molecule of oxygen (O2) forms a double bond, sharing two pairs of electrons, while a molecule of nitrogen (N2) forms a triple bond, sharing three pairs of electrons.

Polarity in Covalent Bonds

• Polarity is a measure of the unequal sharing of electrons, leading to a molecule having a slight charge. This happens when one atom in the bond is more electronegative than the other.
• A polar covalent bond has a slight positive charge on one atom and a slight negative charge on the other.
• This can lead to intermolecular forces such as dipole-dipole interactions in polar molecules. However, in non-polar molecules where the electrons are equally distributed, these attractive forces are minimal.

Covalent Networks

• Some elements like carbon and silicon can form giant covalent structures or covalent networks. These have high melting and boiling points due to the many strong covalent bonds that must be broken.
• An example of a covalent network is diamond, where each carbon atom is covalently bonded to four others in a tetrahedral shape.
• In contrast to simple covalent compounds, covalent networks are hard, have high melting and boiling points, and don’t conduct electricity, except for graphite which can conduct electricity due to delocalised electrons.

Covalent Molecular Structures

• Simple molecular structures are formed by covalently bonded non-metal atoms. These commonly exist as gases, liquids, or solids with low melting points.
• The weak intermolecular forces that exist between simple molecules require little energy to break, hence the low melting and boiling points.
• Examples of simple molecular structures include water (H2O), carbon dioxide (CO2), and methane (CH4).
• Insolubility in water is common with many simple molecular structures, although there are exceptions like sugar and alcohol.