Question

the shining surface of some metals become dull when exposed to Air for a long time give reason​

Answer 1

The metal reacts with air ( oxygen ) to form metal oxide layer on the metal surface, that's why the surface appears dull.

Answer 2

the surface of some metals becomes dull when exposed to air for long time because the metal reacts with air to form metal surface . That is why some metals become dull .......

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