1 Hydrogen
 1 Helium
 2 Lithium
 2 Beryllium
 2 Boron
 2 Carbon
 2 Nitrogen
 2 Oxygen
 2 Flourine
 2 Neon
 3 Sodium
 3 Magnesium
 3 Aluminum
 3 Silicon
 3 Phosphorus
 3 Sulfur
 3 Chlorine
 3 Argon
 4 Potassium
 4 Calcium