Consider the elements selenium (Z = 34), bromine (Z = 35), and krypton (Z = 36). In

Question:

Consider the elements selenium (Z = 34), bromine (Z = 35), and krypton (Z = 36). In their part of the periodic table, the sub shells of the electronic states are filled in the sequence
1s 2s 2p 3s 3p 3d 4s 4p . . . .
What are (a) the highest occupied sub-shell for selenium and
(b) The number of electrons in it,
(c) The highest occupied sub-shell for bromine
(d) The number of electrons in it,
(e) The highest occupied sub-shell for krypton
(f) The number of electrons in it?