In the ground state Kr atom, how many electrons have quantum number l = 0? 8 18 4 2 6 11 9 13 Solution Number of electron in Kr = 36 Electronic configuration is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 l=0 is for s orbital Number of electrons in s orbital = 2+2+2+2 = 8 Answer: 8 .