Question

Which of the subshell designations are possible and which are impossible?

PossibleImpossible

4f

2d

4d

1p

3f

Answer Bank

Answer 1

The subshell designation is made up of two parts - the number part (1, 2, 3, 4 etc.) and the letter part (s, p, d, f etc).

The number part represents the principal quantum numbers and the letter part represents different orbital designations corresponding to the different azimuthal quantum numbers. The orbital designations s, p, d, f represent the azimuthal quantum number of 0, 1, 2, 3 respectively.

Now, the value of azimuthal quantum number is always less than the principal quantum number for any subshell designation. Hence, the subshell designations that abide this rule are possible and the subshell designations that violate this rule are impossible.

For 4f,

principal quantum number = 4

azimuthal quantum number = 3

Thus, azimuthal quantum number < principal quantum number.

Hence, 4f is a possible subshell designation.

---

For 2d,

principal quantum number = 2

azimuthal quantum number = 2

Thus, azimuthal quantum number = principal quantum number.

Hence, 2d is an impossible subshell designation.

---

For 4d,

principal quantum number = 4

azimuthal quantum number = 2

Thus, azimuthal quantum number < principal quantum number.

Hence, 4d is a possible subshell designation.

---

For 1p,

principal quantum number = 1

azimuthal quantum number = 1

Thus, azimuthal quantum number = principal quantum number.

Hence, 1p is an impossible subshell designation.

---

For 3f,

principal quantum number = 3

azimuthal quantum number = 3

Thus, azimuthal quantum number = principal quantum number.

Hence, 3f is an impossible subshell designation.