CH1 - Solid Structures

The lattice is formed by positively andnegatively charged ions. They're arranged in a way to maximise attraction andminimise repulsion.

Crystal co-ordination numbers: 8:8 CsCl and 6:6 NaCl

Very high melting point

Brittle

Insoluble in non-polar solvents, soluble in water

Solid ionic compounds do not conduct electricity, but molten ionic compounds do conduct electricity

A regular lattice of positively charged metal ions surrounded by a sea of delocalised electrons.

Conductors of electricity

High melting and boiling points

Hard

High density

Thermal conductors 

A regular lattice held together by covalent bonds

An allotrope of carbon, a macromolecular crystal

Each carbon is bonded covalently to four other carbon atoms

Tetrahedral arrangement

An allotrope of carbon, a macromolecular crystal

Each carbon atom is covalently bonded to three others, in the same 2D plane, forming layers (covalent hexagon)

Layers are held weakly by van der Waals forces

Strong covalent bonds hold iodine atoms together in the I2 molecule

Weak intermolecular forces hold I2 units together in a molecular crystal

Very high melting point

Only graphite conducts electricity

Insoluble in water

All are hard but graphite is soft