• A formation where the building units are attached to one another in an orderly pattern can be described as a lattice.

•Presence of a formal pattern and the formation from a repetitive basic unit is a common feature of the lattices.

• Various substances with lattice like structures exist in nature. Substances with atoms or molecules or ions arranged in orderly lattice patterns exist.

• Substances with lattice arrangements can be classified according to their building units as follows.               • Homoatomic lattices                                                                                                                                                   • Polar molecular lattices                                                                                                                                             • Heteroatomic lattices                                                                                                                                                 • Ionic lattices                                                                                                                                                                 • Non – polar molecular lattices

• Bonding formed during the formation of the lattice are different, depending on the nature of the building unit of the lattice substance. The nature of the bonding formed during the formation of the lattice affects the physical properties of the lattice.

Homoatomic lattices

Diamond and graphite lattices which are formed from homogeneous atoms are examples for homoatomic lattices.

Lattice arrangement of diamond

Lattice arrangement of graphite

Heteroatomic lattices

• silicon dioxide which is formed from heterogeneous atoms is an example for heteroatomic lattices.

• Homogeneous and heterogeneous atomic lattices are formed by atoms covalently bonding with one another.

• Substances composed of homogeneous and heterogeneous atomic lattices have a high hardness and also higher melting points/ boiling points because such lattices are formed by strong covalent bonds. There is no tendency to go into solution because the covalent bonds present in atomic lattices are very strong.

• Electricity is not conducted through atomic lattices as they lack mobile electrons. (Graphite is an exception)

Non-polar molecular lattice

• Iodine crystals which are formed from non polar iodine molecules are examples for non-polarized molecular lattices.

Lattice arrangement of iodine

• Non polar molecular lattices are built by the bonding of non polar molecules to one another by attractive forces formed between induced dipoles.

• the substances with non polar molecular lattices consisting of molecules bonded to one another by weak Van der Waals forces have a low hardness and their melting points/ boiling points are also low relative to substances formed by other lattices.

• the substances formed by non polar molecular lattices dissolve in non polar solvents because they consist of non polar molecules and they do not conduct electricity as they do not possess mobile electrons.

Polar molecular lattice

• Ice which is formed from polar molecules is an example for polar molecular lattice.

• polar molecular lattices are formed by the bonding together of polar molecules to one another by attractive forces developed between permanent dipoles.

• Substances formed by polar molecular lattices show a high tendency to dissolve in polar solvents but do not conduct electricity due to the lack of mobile electrons

• Substances formed by polar molecular lattices consisting of molecules bonded by permanent dipole – permanent dipole attractive forces (or hydrogen bonds) have a high hardness and also higher melting points / boiling points compared to substances formed by non polar molecular lattices.

Ionic lattice •

Sodium chloride which consists of sodium ions and chloride ions is an example for ionic lattice.

• Ionic lattices are formed by the bonding together of ions by strong electrostatic attractions developed between positively charged and negatively charged ions.

• Substances formed by ionic lattices bonded by strong electrostatic attractions show higher melting points/boiling points and also a high hardness.

• The substances with ionic lattices show a tendency to dissolve in polar solvents.

• The substances consisting of ionic lattices do not conduct electricity in the solid state due to the lack of mobile electrons or mobile ions. The substances with ionic lattices conduct electricity in the molten state or in solution because of the presence of mobile ions.