what is the total number of orbitals associated with principal quantum no. n =3

9

because
3^2 = 9
or because
3 s has 1
3 p has 3
3 d has 5
and 1 + 3 + 5 = 9

Note, each of those orbits can have electrons with spins of + or - 1/2
so total of 18 electrons for n = 3

To find the total number of orbitals associated with a given principal quantum number (n), you can use the formula:

Total number of orbitals = n^2

In this case, n = 3. So, substituting the value of n in the formula, we get:

Total number of orbitals = 3^2
= 9

Therefore, the total number of orbitals associated with principal quantum number (n = 3) is 9.