What is the next atomic orbital in the series below? 1s, 2s, 2p, 3s, 3p, ___

a. 2d

b. 2f

c. 3d

d. 4s

D. 4s this would be the answer because after eight electrons are added to the third orbital two have to be added to the fourth before more can be added to the third one. The third orbital can hold 18 electrons, but it first has to have eight, then two on the fourth orbital, then the rest of the ten can be added