Types of Bonding
- Ionic bonding - Electrostatic attraction between oppositely charged ions in a lattice.
- Covalent Bonding - The electrostatic attraction between a shared pair of electrons and the protons in the nucleii of the bonding atoms.
- Metallic Bonding - The electrostatic attraction between +ve metal ions and a sea of delocalised electrons.
- Simple molecular - IMF's forming bonds between molecules causing them to form a lattice.
ALSO - Dative covalency (lone pair of electrons in a molecule forming bonds with other atoms/molecules) is known as co-ordinate bonding. e.g. NH4+ or NH3BF3
Remember: Covalent bonds between different atoms will be polar to some extent causing non-symmetrical covalent bonds.
e.g. Cl-H where Cl is delta (slightly) -ve due to a higher electronegativity of the Cl causing it to attract electrons more than H which becomes delta +ve
IMF's - Van der Waals Forces (IDIDS)
NB: These instantaneous dipole induced dipole interactions occur in ALL molecules.
There are temporary dipoles due to uneven electron distribution due to the constant movement of electrons, this induces a temporary dipole in a neighbouring molecule, producing a temporary induced dipole-dipole attraction.
The bigger the molecule, (i.e. the more electrons), the greater the IDIDS (and therefore higher mbpts).
- High mbpts due to lots of strong ionic bonds need a lot of energy to break.
- Conduct electricity when molten/solution as ions free to move/carry charge.
- Brittle as if ions shift down, it springs apart due to repulsion of other ions.
- Soluble in water as ions hydrate + form strong IMF's with water
Simple Molecular Crystals
- Low mbpts as weak IMF's between molecules require little energy to break.
- No electrical conductivity as no mobile charge carriers (ions/ free electrons).
- Weak strength due to weak IMF's.
- Soluble in solvents with similar IMF's.
Giant Covalent Crystals
V.V. High mbpts - Each atom bonded to many others (e.g. diamonds tetrahedron) + lots of strong covalent bonds.
No electrical conductivity as no free electrons/ mobile charge carriers.
V. strong strength as each atom bonded to many others (e.g. diamonds tetrahedron).
V.V.High mbpts - Due to lots of strong covalent bonds needing lots of energy to break.
Conducts electricity - Free (delocalised) electrons - mobile charge carriers.
Strong within layers, weak (soft) between layers - Due to lots of strong covalent bonds needing lots of energy to break but only idids between layers.
Insoluble due to strong covalent bonds.
Medium mbpts - Electrons are mobile allowing conduction of heat through ions.
Electrical conductivity when solid/molten - sea of de-localised electrons in these states.
Medium strength - Mobile electrons allow ion layers to slide over each other.
Insoluble - Strong lattice don't form bonds with solvents.