How many orbitals can exist at the third main energy level

a. 3

b. 6

c. 9

d. 18

The answer would be D, 18.

The energy level have different kinds of orbitals each orbital contain 2 electrons

So every orbital denoted as n2

Where when we consider 3rd energy orbital n = 3

Which is equal to 9 so third energy level has 9 orbital

So correct answer is (c)