31. Reactivity with halogens: EX2 EX4 and EX6
The stability of halides decreases in the order F- > Cl- > Br- > I-. This is because E-X bond length increases with increase in size.
Among hexa halides, fluorides are the most stable because of steric reasons.
Dihalides are sp 3 hybridised, are tetrahedral in shape.
Hexafluorides are only stable halides which are gaseous and have sp 3 d 2 hybridisation and octahedral structure.
H2O is a liquid while H2S is a gas. This is because strong hydrogen bonding is present in water. This is due to small size and high electronegativity of O.
32. Oxygen: Preparation:
Heat 2KClO 3 → 2KCl + 3O 2 MnO2 finely divided metals
2H2 O2( aq) → 2H2 O( l) + O2( g)
heat 2Ag2O( s) → 4Ag( s) + O2( g)
2HgO( s) → 2Hg( l) + O2( g)
2Pb3O4( s) → 6PbO( s) + O2( g)( Red lead)
2PbO2( s) → 2PbO( s) + O2( g)