The maximum number of electrons that can occupy the shell having a principal quantum number 3 is

39. The maximum number of electrons that can occupy the shell having a principal quantum number 3 is

A. 3

B. 9

C. 10

D. 18

E. 32

The correct answer is D. 18

Solution:The principal quantum number, which is given by symbol n, has positive values like, 1,2,3,....,etc. It determines the size and the energy of the orbital. Orbitals that have the same value of the principal quantum number form a shell. 

The formula often used is given as 2n^2

Substitute the given value into the formula.

2(3)^2= 2(3*3)

=2*9= 18

Thus when n=3, maximum number of electrons = 18.

QUESTION SOURCE: 2001 NECO OBJECTIVE  QUESTION 38.

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