4. Bonding

The electrostatic attraction between oppositely charged ions • Cations: positive charge, lose valence electrons (metals) • Anions: negative charge, gain valence electrons (non-metals)

• non directional bond - strength of bond eaqual in all directions • conducts electricity when molten/ in solution • high melting/ boiling points • hard solids • low volatility

The electrostatic attraction between a pair of electrons and positively charged nuclei • bonding electron pairs • electrons not involved in bonding are called non-bonding e- pairs

• Covalent - high electronegativity locks the electrons in covalent bonds • Metalic - Low electronegativity allows electrons to float in seas • Ionic - high electronegativity difference means uneven sharing < 0.4 ——————————————— 1.8< nonpolar polar ionic covalent bond covalent bond

• Partial positive charge (positive/ negative) • The overall charge = Dipole movement • The molecular is polar if the electron densities are not symmetrical (eg H2O)

• electrostatic attraction between positive and negative ions • the smaller the ions / the greater the charge on the ions, the stronger the attraction between the ions • greater charge density within the structure

• shared pair of electrons between atoms • the shorter the bond, the stronger it is • triple bonds are shorter and stronger than double bonds • triple > double > single

• attraction between lattice of positive metal ions and delocalized outer shell electrons • the smaller the metal ions, the greater the charge on ions • the more delocalised outer shell electrons there are, the stronger the attraction between the ions and electrons • greater charge density within the structure

• representations of molecules showing all electrons, bonding and nonbinding • each bond contains 2 electrons • elements pair up according to the octet rule

• Boron - forms stable compounds with just 3 valence electrons • highly reactive • Beryllium - forms stable compounds with just 2 valence electrons • compounds that break the octet rule are often toxic and dangerous, ready to react so the octet rule is obeyed

Valence Shell Electron Pair Repulsion Electron domain - the number of bonds/ electron pairs there are on the central atom

If a molecule / ion has lone pairs on the central atom, the shapes are slightly distorted away from the regular shapes because of extra repulsion caused by the lone pairs

180

105

120

107

109.5

90

When a lewis structure allows for the same arrangement of atoms but a different but equally valid arrangement of electrons, resonance occurs • Electrons are delocalized and are spread over 2 bonding orbitals • Located in the p orbitals - overlapping p orbitals create pi bonds with delocalized electrons

Compounds of the same element that differ in structure eg Carbon

• Each carbon bonded to 4 other carbons by sp3 hybridization • High melting point • strong directional covalent bond • Extremely hard • difficult to break atoms apart/ move them in relation to one another • No electrical conductivity • electrons are localized in specific bonds • Insoluble in polar and non-polar solvents because molecular bonds are stronger than any IMF

• Carbon atoms bonded via sp2 hybridization • form sheets of 6 sided rings with p-orbitals perpendicular from plane of ringt • presence of p orbitals allows for stronger london forces that hold the sheets together

• Conducts electricity - delocalized electrons • Slippery - sheets can slip past each other • High melting point - delocalized electrons • Insoluble

Buckyballs • carbon atoms bond in units of 60 atoms, with interlocking 6 sided and 5 sided rings • sp2 hybridization - extra p orbitals form pi bonds resulting in the properties Properties • Super strong • conduct electricity and heat with low resistance • free radical scavenger