why is alminium oxide insoluble in water whereas sodium chloride is soluble?
Aluminium oxide has more covalent character, so is less likely to dissociate in water. Sodium chloride is very ionic, so easily dissociates in water. I hope you know what I mean by covalent. Edit: “Bonded ionically” – I’m afraid, particularly in GCSE/A-level, what they tell you about bonding is an over-simplification. In reality bonds aren’t just “ionic” or “covalent”, but somewhere inbetween. Traditional ionic compounds (like your NaCl) tend to have polar bonds, with the electrons lying closer to one of the bonded species than the other (closer to Cl in the NaCl case). Covalent compounds have the electrons distributed towards the centre of the bond. The distribution of electrons in the bond is to do with a factor called electronegativity. Electronegativity is a measure of how well an atom attracts electrons to itself. Two atoms with a large difference in electronegativity form very polar (ionic) bonds. The Pauling electronegativity values in this case are: Al (1.61) O (3.44) (differen
