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Covalent Bonding [print-friendly version]
- Found in most non-metal elements (except C and Si) and most compounds of non-metals e.g. H2O, CO2, NH3, C2H5OH etc.
- Covalent Molecular substances exist in discrete groups of atoms called molecules - all molecules of a particular substance are identical. Adjacent atoms in molecules share electrons.
- Covalent bonding is the strong electrical attraction between the nuclei and their shared electrons. This very strong form of bonding occurs within the molecule, (intra-molecular force).
- Attractions between molecules (inter-molecular) are weak and are referred to as weak intermolecular forces, weak Van der Waals forces, or weak dispersion forces.
- Since two distinct forms of attraction exist in solid covalent molecular substances, (i.e. strong covalent bonding within the molecule and weak inter-molecular forces between molecules), the lattice of a covalent molecular substance is said to be discontinuous. Positions within the regular lattice of a covalent molecular solid are occupied by molecules.
- Atoms that share one pair of electrons - single covalent bond
- Atoms that share two pairs of electrons - double covalent bond
- Atoms that share three pairs of electrons - triple covalent bond
Property |
Explanation |
Non-conductors of electricity (in solid, molten or aqueous solution) |
The molecules are uncharged and electrons are held tightly within covalent bonds. \ There are no mobile charged particles to conduct electricity. [Exception: some covalent molecular substances react with water to form ions and thus do become conductors in aqueous solution - e.g. acids, ammonia…] |
Low melting point and boiling point. |
When covalent molecular substances melt a small amount of thermal energy is needed to overcome the weak inter-molecular forces, (Van der Waals forces) between the molecules. |
Soft solids |
Weak forces exist between molecules therefore little effort is required to separate the molecules. |
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