(a) How many sub-shells are associated with n = 4?

(b) How many electrons will be present in the sub-shells having ms value of –1/2 for n = 4?

(a) n = 4 [Given]

For a given value of ‘n’, ‘L’ can have values from zero to [n-1].


∴ L = 0, 1, 2, 3


Thus, four sub-shells are associated with n = 4, which are s, p, d and f.


(b) Number of orbitals in the nth shell = n2


For n = 4


Number of orbitals = 16


Each orbital has one electron with ms = -1/2


Hence there will be 16 electrons with ms = -1/2


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