2.2.2 bonding and structure

Electrostatic attraction between oppositely charged ions formed by electron transfer Giant ionic lattice Ionic bonding between ions

High melting points - strong electrostatic forces between oppositely charged ions in lattice - higher when ions are smaller and/or have higher charges Non conductor of electricity when solid - ions held together tightly in lattice and can’t move so no charge conducted Good conductor of electricity when in solution or molten - ions are free to move when in solution and molten so can carry a charge Usually soluble in aqueous solvents

Strong electrostatic attraction between a shared pair of electrons and nuclei of bonded atoms

When the shared pair of electrons in covalent bond come from only one of the bonding atoms Aka co-ordinate bonding E.g. NH4+, H3O+, NH3BF3

Measurement of covalent bond strength The larger the value, the stronger the covalent bond

Simple molecular Intermolecular forces (induced/ permanent dipole-dipole/ hydrogen bonds) between molecules E.g. iodine, CO2, H2O

Low as weak intermolecular forces between molecules (specify type)

Poor as no ions to conduct and electrons are in fixed positions so cannot move to carry a charge

2 BP, 0 LP 180

3BP, 0LP, 120

4BP, 0LP 109.5

3BP, 1LP 107

2BP, 2LP 104.5

6BP, 0LP 90

State no. BP + LP State electron pairs repel and try to get as far apart as possible If no LPs, state electrons repel equally If there are LPs, then state LPs repel more than BPs State actual shape and bond angle

Repel more than bonding pairs Reduce bond angles by 2.5 per lone pair

Relative tendency of an atom in a covalent bond in a molecule to attract electrons towards itself in a covalent bond

F, O, N, Cl

Increase across a period as proton number increases atom radius decreases as electrons are in the same shell

Decreases down a group as distance between nucleus and outer electrons increases Shielding of inner shell electrons increases

When the elements in the bond have different electronegativities When there is an unequal distribution of electrons in the bond, a dipole forms. Element with the larger electronegativity will have the negative dipole

Will not be polar even if all individual bonds are polar No net dipole

All molecular substances and noble gases, not in ionic

In any molecule the electrons are moving constantly and randomly As this happens electron density fluctuates and parts of the molecule become more or less negative Temporary dipoles from this cause dipoles to form in neighbouring molecules (induced dipoles)