Bonding

• An ionic structure is formed when positive metal ions are attracted to negatively charged non metal ions.
• Ionic structures form giant lattices of ions.
• Ionic structures have high melting points as they form a giant lattice of ions in which there is very strong electrostatic attraction between the positive and negative ions, so a lot of energy is needed to overcome this.
• When solid, ionic structures cannot conduct electricity as the ions are fixed in a giant lattice structure. However, when molten or dissolved, the ions are free to move and can carry charge.
• Ionic structures dissolve well in polar solvents e.g. water as the polar solvent molecules attract ions out of the lattice and into the solution.
• Ionic structures are brittle as the layers in the giant ionic lattice cannot easily slide over each other, and if they do, ions of the same charge repel each other and the structure breaks down.
• In a metallic structure, positive ions are packed into a lattice. The outer shell electrons are not bound to an individual atom, and they can move around between layers.
• Metallic structures can conduct electricity because the delocalised electrons can move freely around the lattice and carry charge.
• The strength of metallic bonding depends on the charge of an ion and the size of an ion. Greater charge, stronger attraction. Smaller ion, stronger attraction.
• Metallic structures are malleable and ductile as the layers of ions can slide over each other as they are all positive ions and the delocalised electrons are free to move.
• Definition of covalent bonding

  A bond formed by a shared pair of electrons.
• In giant covalent structures, atoms are linked together by strong covalent bonds to form a giant crystal lattice. This can occur in elements and compounds.
• Graphite is the only giant covalent structure to conduct electricity as the carbon atoms only use three of its outer electrons to bond with other carbon atoms, meaning there are delocalised electrons that can carry charge.
• Graphite has a high melting point due to the strong covalent bonds between the atoms on the individual layers.
• Graphite is soft as there are weak van der Waals' intermolecular forces between layers, so they can slide over each other.
• A dative covalent bond is a bond formed by a shared pair of electrons where both electrons come from one atom.
• Electronegativity is the power of an atom to attract the electron pair in a covalent bond.
• The pair of electrons isn't always shared equally, one atom will attract the pair more than the other, based on its electronegativity.
• van der Waal's are forces between molecules and atoms.
• van der Waals are only intermolecular in diatomic gases, monoatomic gases, alkanes.
• Size of van der Waals depends on size of molecule and atom, and the amount of branching.
• Permanent dipole-dipole intermolecular forces are produced when atoms have different electronegativities.
• Hydrogen bonding is the strongest, it occurs between a lone pair on N O F and a hydrogen atom.
• Hydrogen bonding is only with N O and F as they are the most electronegative atoms, so the partial negative and positive charges are very strong.