The number of orbitals in a p-sub level of an atom is

Analyze the question

You are asked how many orbitals make up a p sub-level (p sub-shell) in an atom.

Explain the concept

Each sub-level has a fixed number of orbitals, determined by the azimuthal (angular momentum) quantum number, l:

• Number of orbitals in a sub-level = 2l + 1
• Each orbital holds a maximum of 2 electrons (with opposite spins).

| Sub-level | l | Orbitals (2l + 1) | Max electrons | |-----------|---|-------------------|---------------| | s | 0 | 1 | 2 | | p | 1 | 3 | 6 | | d | 2 | 5 | 10 | | f | 3 | 7 | 14 |

Show the solution

For the p sub-level, l = 1:

Number of orbitals = 2(1) + 1 = 3

These three orbitals are px, py and pz. They are oriented along the x, y and z axes, so they are at right angles to each other.

Check against the options

• A (2): this is the number of electrons an orbital can hold, not the number of orbitals.
• B (3): correct.
• C (5): this is the number of d orbitals.
• D (6): this is the maximum number of electrons in the p sub-level (3 × 2), not the number of orbitals.

Exam tip

Remember the pattern 1, 3, 5, 7 for s, p, d, f orbitals. Multiply by 2 to get the maximum electrons: 2, 6, 10, 14. WASSCE often tests the difference between "number of orbitals" and "number of electrons", so read the question carefully. Option D (6) is the trap here.