Hi,
Let me walk you through this: Try and remember these two sets of three basic facts (the first set (A = oxidation) of three facts are the opposite of the 2nd set (B = reduction) of three facts (trying to make it easy for you to understand and to remember!):-
A. Oxidation occurs when any of these happen:
1. Addition of oxygen
2. Removal of hydrogen
3. Loss of an electron
B. Reduction occurs when any of these happen:
1. Removal of oxygen
2. Addition of hydrogen
3. Gaining an electron
NOW TO ANSWER YOUR Q.
When copper is oxidised to copper oxide:
2Cu + O2 -------> 2CuO
Oxygen is added to copper, so from A(1) above oxidation of copper occurs. (Happy with this? Gd well done!)
Also because copper is going from Cu (uncharged copper atom - if you touch your mum's copper saucepan, you do not get an electric shock, do you - no, so copper metal is uncharged, with me?) to Cu+ (one positive charge is present - how did that happen - yes, cool - the copper atom lost an electron (one minus) so it is left with one plus. The item in bold in the previous sentence (look at A(3) above again) tells us that oxidation has taken place.
IF YOU GET THIS type of Q in exam, look at how many marks it is worth (they always tell you these days!) - if it is worth one mark, just say point A(1) - if it is worth 2 marks, say BOTH A(1) and A(3).
Easy peasy lemon squeezy, correct?
M