If element with principal quantum no n>4 were not allowed in nature , then the no of possible elements would be 1)60. 2)32. 3)4. 4)64

N=1 present K-shell and the number of elements having K shell=2 N=2 present L shell and the number of element having L shell=8 N=3 present N shell and the number of elements having N shell = 18 N=4 present N shell and the number of elements having N shell = 32 Total number = 2+8+18+32=60

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n=4 we know acc to bohr's theory element =2n^2 2×16=32 2+8+18+32=60

Main reason behind these numbers is bohrs atomic theory which gives correct explanation about elements present in different values of n

According to Bohr theorem number of electron in that particular orbital is 2(n)^2 ....So for n less than 4 . 2+8+18+32=60