Why do silver things turn black after some time, why does gold not have any such effect?

Have you ever seen the silver puja plate or anklets of your home which turn black after a few months? Whereas a gold ring or necklace remains shining with the same shine for years.

This difference is not just of color or price, but of the chemical nature of the metals. Actually, silver is a metal which reacts quickly with sulfur compounds present in the air.

Especially, from hydrogen sulphide gas present in the air. When this gas comes in contact with the silver surface, a chemical process occurs that forms silver sulfide (Ag₂S). This layer gradually turns the silver black.

This process is called Tarnishing, i.e. accumulation of a chemical layer on the surface of silver, which covers its shine. Surprisingly, this gas comes out from common things around us, like pollution, dust, rubber, perfume, detergent, even some amount of sulfur is found in human sweat.

Therefore, the silver which is used a lot turns black quickly, while the things kept in the cupboard get affected a little later.

Gold is a chemically very stable metal. This means that it rarely or almost never reacts with any gas or oxygen.

The oxygen, moisture or sulfur present in the air does not have any significant effect on it. Therefore, neither sulphide nor oxide is formed on the surface of gold, due to which it retains its shine and color for years.