chemisy

To extract magnesium (Mg) and aluminum (Al) metals, electrolysis of their molten ores is applied because they are reactive, which form stable ores.
2Al2O3 --- > 4Al + 3O2
2MgO --- > 2Mg + O2
To extract iron metal (Fe), reduction with carbon monoxide, carbon or hydrogen is applied as iron is less reactive and its ore is less stable.
Fe2O3 + 3CO --- > 2Fe + 3CO2
Fe2O3 + 3C --- > 2Fe + 3CO
Fe2O3 + 3 H2 --- > 2Fe + 3H2O
To extract mercury metal (Hg) from its ores, direct heating is applied as their ores are unstable and can decompose on direct heating.
2HgO --- > 2Hg + O2
For gold (Au), it exists as free element and no extraction is needed.

Alminium to copper is use electrolysis in ECS

Hg is only heat the ore.

Gold(Au) is use plysical method

ECS is K>Na>Ca>Mg>Al>Zn>Fe>Pb>H>Cu>Hg>Ag>Au=Pt