What is the maximum number of electrons allowed in the third energy level

18 electrons allowed in the 3rd energy level

The maximum number of electron in the first energy level (n = 1) is 2 (1) 2 = 2 electrons. The maximum number of electron in the second energy level (n = 2) is 2 (2) 2 = 8 electrons. The maximum number of electron in the third energy level (n = 3) is 2 (3) 2 = 18 electrons ... etc ...