(1) Occurrence and extraction of mercury: Cinnabar (HgS) is the only important ore of Hg. It is concentrated by froth floatation method and mercury is extracted from this ore by heating it in air at 773-873 K (auto reduction).

                 _273-873K

The mercury vapours thus obtained are condensed to give liquid metal. Hg thus obtained contains impurities of Zn, Sn and Pb. These are removed by treating the impure metal with dil HNO₃ , mercurous nitrate, Hg₂ ( NO₃ )₂ thus formed react with metals present as impurities forming their nitrates which pass into solution leaving behind pure mercury. However, it is best purified by distillation under reduced pressure.

                                       _warm

Similar reaction is given by Pb and Sn.

Properties of mercury : Mercury is less reactive than Zn. It is a liquid at room temperature and has low thermal and electrical conductivity. Mercury forms dimeric mercury (I) ions, Hg⁺²₂ in which the two atoms are bonded by a covalent bond. It is slowly oxidised to HgO at about its boiling point. Hg does not react with dil. HCl or dil. H₂SO₄ but reacts with hot concentrated H₂SO₄ to form HgSO₄ , it reacts with both warm dil. and conc. HNO₃ evolving NO and NO₂ respectively.

Hg + 2H₂SO₄ ( hot, conc. ) → HgSO₄ + SO₂ + 2H₂O

Hg + 4HNO₃ ( conc. ) → Hg ( NO₃ )₂ +2NO₂ + 2H₂O

Hg does not react with steam or water hence can’t form any hydroxide.