A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed.

Explanation

The brown coloured element .X. is copper. On heating in air it forms copper oxide which is black in colour.
`underset("(Brown colour)")underset("Copper")(2Cu(s))+underset("Oxygen")(O_(2)(g))tounderset("(Black)")underset("Copper oxide")(2CuO(s))`