1. The problem statement, all variables and given/known data This isn't really a homework question, but it is part of a lecture powerpoint that the teacher will go through with on Monday and I was just getting ahead so I can understand better. [PLAIN]http://img59.imageshack.us/img59/3088/cuelectronconfig.png [Broken] 2. Relevant equations NONE 3. The attempt at a solution I thought it would be the first one because 4s^2 has a higher energy level so I thought that copper would be more stable. I'm not sure if I'm understanding the wording correctly. So I don't know the correct answer but I hope someone can help me understand.