Question: how many electrons are in the second principal energy level of nitrogen?
Answer: A principal energy level may contain up to 2n2 electrons, with n being the number of each level. The first energy level can contain 2(1)2 or two electrons; the second can contain up to 2(2)2 or eight electrons; the third can contain up to 2(3)2 or 18 electrons, and so on.