Cemistry Revision

Structures and Propertres

Ionic Compound

• Conisists of a giant structure of ions arranged in a lttice
• Attractive electrostatic forces between the oppositely charged ions act in all directions and are very strong
• These forces holds the ions in the lattice togehter very tightly
• It takes alot of energy to break the lattice apart meanining that ionic compounds have very high melting and boiling points
• If the lattice has been broken, the ions are free to move and the ionic solid becomes a liquid - the ions are free to move through the molten liquid
• A solid ionic compound can't conduct electricity because each ion is held in a fixed position in the lattice and are unable to move around - they can only vibrate
• Many ionic compunds can dissolve in water
• when this happens the lattice is split up by the water molecules
• When the ions are free to move around in an ionic compoud it is able to conduct electricity

Ionic Compounds

Basically....

Ionic Solid: Ions fixed in lattice - doesn't conduct electricity

Molten Ionic Compound:High temperature provides energy to overcome strong attractive foreces between ions, ions are free to move so will conduct electricity

Ionic compound in solution: Water molecules separate ions from the lattice, ions are free to move so will conduct electricity

Simple Molecules

• Covalent molecules are non-metals which react to form compounds by sharing electrons in their outer shell
• Substances made from covalent bonding, have low melting and boiling points
• This means that many simple molecules are liquid or gas at room temperature
• Covalent bonds are very strong
• Atoms within each molecule are held very tightly together
• Each molecule tens