why copper and silver occur in free as well as combined form while sodium potassium calcium etc are found in combined form ?

Dear Student, The metal found in nature and which occurs both in the free and the combined state is generally known as the pure metals. Those metals which exists both in free and combined state are: • Copper • Silver Silver exists as AgCl, Ag2O, AgNO3, and many more. Copper exists as Coppersulphide (Cu2S), CuO and Cu2O. Sodium, Potassium and Calcium like metals are present in the top of the reactivity series of metals, that is they are very reactive. They are so reactive that they react with atmospheric gases and surrounding elements and form compounds that is why they are not found in free state. Elements Ore components K = KCl, K2SO4, etc. Na = NaCl, Na2CO3, NaHCO3 Ca = CaCO3, CaCl2, CaSO4 Regards,