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

Copper is a brown coloured shiny element, when heated in air, it becomes black in colour.
$$ 2Cu + O_{2} + Heat \rightarrow 2CuO $$ Hence, the element ‘X’ is copper and black coloured compound formed is copper oxide.