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

Copper metal is the shining brown element (Cu). The metal reacts with atmospheric oxygen when heated in air to produce copper oxide. Thus, the substance that is black in colour is copper oxide.

2Cu(s) + O2(g) → 2CuO(s)