Question: how many electrons are there in the second principal energy level of a phosphorus atom
Answer: of electrons / shell Group Hydrogen Helium 18 Lithium 2 , 1 Beryllium 2 , 2 5 Boron 2 , 3 13 6 Carbon 2 , 4 14 7 Nitrogen 2 , 5 15 8 Oxygen 2 , 6 16 9 Fluorine 2 , 7 17 10 Neon 2 , 8 18 11 Sodium 2 , 8 , 1 12 Magnesium 2 , 8 , 2 13 Aluminium 2 , 8 , 3 13 14 Silicon 2 , 8 , 4 14 15 Phosphorus 2 , 8 , 5 15 16 Sulfur 2 , 8 , 6 16 17 Chlorine 2 , 8 , 7 17 18 Argon 2 , 8 , 8 18 19 Potassium 2 , 8 , 8 , 1 20 Calcium 2 , 8 , 8 , 2 21 Scandium 2 , 8 , 9 , 2 22 Titanium 2 , 8 , 10 , 2 23 Vanadium 2 , 8 , 11 , 2 5 24 Chromium 2 , 8 , 13 , 1 6 25 Manganese 2 , 8