Question: how many electrons are there in the 2nd principal energy level of a phosphorus atom?
Answer: Phosphorus has a filled 2nd principal energy level. The 2nd principal energy level can only hold 8 electrons, 6 in the p orbitals and 2 in the s orbital. Phosphorus has a partially filled 3rd principal energy level with 2 electrons in the 3s and one in the 3p orbital. So the answer is 8.