If elements with principal quantum number n greater than four were not allowed in nature, then number of elements would be:

Options

A. 60
B. 32
C. 4
D. 64

Answer

A

Explanation

Upto quantum number 4, an atom has K,L,M and N shells..
Maximum number of electrons in a shell `=2n^(2)`
Thus, there are 2 electrons in K-shell (n=1)
and 8 electron in L-shell (n=2)
18 electron in L-shell (n=2)
18 electron in M- shell (n=3)
and 32 electron in N-shell (n=4)
Total number of electrons =2+8+18+32=60