What type of reaction is 2Cu O2---2CuO?

The reaction ( 2\text{Cu} + \text{O}_2 \rightarrow 2\text{CuO} ) is a combination (or synthesis) reaction, where two or more reactants combine to form a single product. In this case, copper (Cu) reacts with oxygen (O₂) to produce copper(II) oxide (CuO). This type of reaction typically involves elements or simpler compounds coming together to form a more complex compound.