Question

Giving suitable examples, explain how the reactivity of a metal is related to its mode of occurrence in nature.

Answer 1

The mode of occurrence of metals in the earth’s crust depends on their reactivity.

1. Highly reactive metals (K, Na, Ca, Mg, Al): These metals readily combine with oxygen, halogens and other non-metals. They occur in nature only as stable compounds (oxides, halides, carbonates).
   Example: Na as NaCl (rock salt), Al as Bauxite (Al₂O₃ . 2H₂O).
2. Moderately reactive metals (Zn, Fe, Pb, Cu): They are less reactive than alkali and alkaline earth metals. They occur as oxides, carbonates and sulphides.
   Example: Fe as Haematite (Fe₂O₃), Zn as Zinc blende (ZnS), Pb as Galena (PbS).
3. Least reactive or noble metals (Ag, Au, Pt): They are chemically least reactive and resist oxidation and corrosion. They are found in the native (free) state.
   Example: Gold, Platinum, Silver.