Question

how can justify that 4 th proid ha 18 elements
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Answer 1

Answer:

When n = 4, These orbital 3d, 4s and 3p present as outermost shell shows the filling in order of their increasing energies in an order of 3p<4s < 4d . ... Thus maximum number of electrons that can occupy theres three orbital are 18 thus we can say that 18 elements should be present in 4th period.