2.2.2

High melting & boiling points Strong electrostatic forces - large amounts of energy needed to break Electrostatic forces - hold opposite charged ions together , why ionic compounds have high mp & bp

Ions in fixed position, cannot move Non-conductor of electricity

Solid lattice breaks down & ions free to move Ionic compound now a conductor of electricity

Dissolves in polar solvents (e.g. water) Polar water molecules break down lattice by surrounding each ion to form a solution

Solid ionic compound exist as giant ionic lattices Strong electrostatic attraction between opp charged ions result in a high melting point

E.g. OH-, SO42- Have covalent bonds within polyatomic ons Form ionic bonds with other ions

When one/both ions have a high charge and are small MgO > NaCl as Mg=2+, O=2-

Covalent bonding

Ionic

Stable electron configuration Full outer shell so, very stable

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

2 shared pairs of electrons 3 shared pairs of electrons

One of the atoms supplies both the shared electrons for the covalent bond E.g. ammonium ion, NH4+ Nitrogen atoms donates a pair of electrons to a proton (H+ ion)

Energy needed to break one mole of a particular bond Always exothermic Larger the value of the bond enthalpy, the stronger the covalent bond

An atom may become charged when the number of electrons is altered (loss or gain of electrons) This charged atom is called an ion

Lose electrons > cations (pos charged ions)

Gain electrons > anions (neg charged ions)

Occurs due to strong electrostatic forces of attraction between pos and neg charged ions

Existing as a single atom (group 0)

Full outer shell typically with 8 electrons

2n2 n - principle quantum number

Acceptor molecule must be electron deficient (available orbitals for the electron to occupy)