The metals at the bottom of the activity series are least reactive. They are often found in free state. E.g. Gold, silver, and copper. But copper and silver are also found in combined state as their sulphide or oxide ores. E.g. copper which is found as Cu2S in nature can be obtained from its ore by just heating in air.

2Cu2S + 3O2 ------> 2Cu2O + 2SO2
2Cu2O + Cu2S -----> 6 Cu + SO2
 Similarly, cinnabar is an ore of mercury. When it is heated in air, it is first converted into mercuric oxide ( HgO). Mercuric oxide is then reduced to mercury on further heating.
2HgS + 3O2 ----> 2HgO + 2SO2
3 4 3
Extraction of Metals of Least Reactivity

Mercury and copper, which belong to the least reactivity series, are often found in the form of their sulphide ores. Cinnabar (HgS) is the ore of mercury. Copper glance (Cu2S) is the ore of copper.

Extraction of mercury metal: Cinnabar (HgS) is first heated in air. This turns HgS [mercury sulphide or cinnabar] into HgO (mercury oxide); by liberation of sulphur dioxide.

Mercury oxide so obtained is again heated strongly. This reduces mercury oxide to mercury metal.

2HgS + 3O2 ⇨ 2HgO + 2SO2

2HgO ⇨ 2Hg + O2