Never mind I figured it out. A supply of copper pipes is stored outdoors. Over the course of many years, the copper reacts with oxygen and turns green. What clue indicates a chemical reaction took place? copper reacts with oxygen

Use this information to determine the number of calends electrons in the atoms. which of the following correctly compares the stability of the two atoms? a) both are unreactive b) both are highly reactive c) a is unreactive and d is reactive d) a is reactive and d is unreactive