BONDING

Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer.

Metal atoms lose electrons to form +ve ions. Non-metal atoms gain electrons to form -ve ions.

Ionic crystals have the structure of giant lattices of ions

Ionic bonding is stronger and the melting points higher when the ions are smaller and/ or have higher charges. E.g. MgO has a higher melting point than NaCl as the ions involved (Mg2+ & O2- are smaller and have higher charges than those in NaCl , Na+ & Cl- )

Positive ions are smaller compared to their atoms because it has one less shell of electrons and the ratio of protons to electrons has increased so there is greater net force on remaining electrons holding them more closely.

The negative ion has more electrons than the corresponding atom but the same number of protons. So the pull of the nucleus is shared over more electrons and the attraction per electron is less, making the ion bigger.

Within a group the size of the ionic radii increases going down the group. This is because as one goes down the group the ions have more shells of electrons.

A covalent bond is a shared pair of electrons

A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms

Metallic bonding is the electrostatic force of attraction between the positive metal ions and the delocalised electrons

• Number of protons/ Strength of nuclear attraction. The more protons the stronger the bond • Number of delocalised electrons per atom (the outer shell electrons are delocalised). The more delocalised electrons the stronger the bond • Size of ion.The smaller the ion, the stronger the bond.

*mostly liquids and gases *it has intermolecular forces (van der Waals, permanent dipoles, hydrogen bonds) between molecules *Iodine , Ice ,Carbon dioxide,Water,Methane

• solids • its a giant molecular structure • Diamond,Graphite,Silicon dioxide,Silicon

• Giant metallic lattice • shiny metals • malleable as the positive ions in the lattice are all identical.so the planes of ions can slide over one another

high- because of giant lattice of ions with strong electrostatic forces between oppositely charged ions

low- because of weak intermolecular forces between molecules (specify type e.g van der waals/hydrogen bond)

high- because of many strong covalent bonds in macromolecular structure. Take a lot of energy to break the many strong bonds.

high- strong electrostatic forces between positive ions and sea of delocalised electrons

ionic compounds-generally good simple molecular substances-generally poor macromolecular substances-insoluble metal-insoluble

solid: poor-ions cant move as its fixed in a lattice molten: good-ions can move

solid: poor-no ions to conduct and electrons are localised molten: poor-no ions

solid:diamond-poor as electrons can’t move(localised) graphite-good as free delocalised electrons between layers molten:poor

solid: good-delocalised electrons can move throughout structure molten: good

• crystalline solids • giant ionic lattices • sodium chloride,magnesium oxide