Angular Momentum Quantum Number Calculator

Choose a mode for your quantum data. See angular momentum magnitude, parity, and allowed states. Download results to share, review, or study later easily.

Calculator

Choose a mode. Enter values. Submit to see results below the header.

Some modes use different symbols: subshell letter maps to l, while term letter maps to L.
Used in “From n” and “Validate”. Range: 1 to 30.
Used in “From l” and “Validate”. Range: 0 to 20.
Maps to l: s=0, p=1, d=2, f=3.
Maps to total orbital L: S=0, P=1, D=2, F=3.
Provide |L| in ħ or J·s, depending on unit.
ħ = 1.054571817×10⁻³⁴ J·s (used internally).

Example Data

n l Subshell |L| (ħ) Orbitals (2l+1) ml range
20s010 to 0
31p1.41421363-1 to 1
42d2.44948975-2 to 2
53f3.46410167-3 to 3

Formula Used

For orbital angular momentum, the quantum number l is a non‑negative integer. The magnitude of angular momentum is:

|L| = √(l(l+1)) · ħ

The magnetic quantum number has allowed values:

ml = −l, …, 0, …, +l    (count = 2l+1)

How to Use This Calculator

  1. Select a mode that matches your known data.
  2. Enter the relevant value(s), such as l or n.
  3. Press Calculate to show results under the header.
  4. Use the download buttons in the results box for CSV or PDF.
  5. For “From |L|”, choose the correct unit (ħ or J·s).

Angular Momentum Quantum Number in Practice

1) Why the l value matters

The angular momentum quantum number l tells you how an orbital depends on angle. It separates orbital “families,” influences angular nodes, and helps label spectra. Once l is known, you can immediately count allowed orientations and predict parity behavior.

2) Allowed l values for a given n

For each principal quantum number n, l must be an integer from 0 to n−1. Example: n=3 allows l=0,1,2; n=4 allows l=0,1,2,3. The “From n” mode lists every allowed l and the matching subshell letter. Validator mode confirms it quickly.

3) Subshell letters and conversion

Subshell letters are shorthand for l: s→0, p→1, d→2, f→3. Higher labels continue alphabetically (skipping j), so g→4, h→5, i→6. The letter mode converts the label to l and then reports orbitals and ml range. This is useful when a table lists orbitals by letter only.

4) Magnitude of orbital angular momentum

Quantum mechanics quantizes L², not L, so L² = l(l+1)ħ². Therefore the magnitude is |L| = √(l(l+1))ħ. The calculator shows |L| as a multiplier of ħ and also in J·s using ħ = 1.054571817×10⁻³⁴. Reporting both forms helps when unit systems differ across sources.

5) Magnetic quantum number and degeneracy

For a given l, the magnetic quantum number ml takes integer values from −l to +l. That produces 2l+1 distinct orientations and equals the number of orbitals in the subshell. Example: l=2 gives five orbitals and ml=−2,−1,0,1,2. With electron spin included, the maximum electron capacity doubles.

6) Parity and quick rule checks

Orbital parity depends on l as (−1)l: even l gives even parity and odd l gives odd parity. Parity is commonly referenced in transition discussions because many electric-dipole processes require a change in l. A common classroom rule is Δl = ±1 for such transitions. Seeing parity beside l helps you sanity-check results faster.

7) Term letters, total L, and using |L| mode

Uppercase term letters (S, P, D, F…) represent total orbital angular momentum L in LS coupling, not a single-electron subshell l. If you know a magnitude, the tool solves l(l+1)=(|L|/ħ)² to estimate l and shows the nearest integer. Choose the correct mode to avoid mixing l and L.

FAQs

1) What does l measure in an orbital?

It labels the orbital’s angular behavior and shape family. It is tied to the eigenvalue of L² and influences nodes, degeneracy, parity, and many spectroscopy notations used in electron configurations.

2) What l values are allowed for a given n?

For a principal quantum number n, l can be any integer from 0 to n−1. Example: n=4 allows l=0,1,2,3. The validator mode checks this rule instantly.

3) Why is |L| equal to √(l(l+1))ħ?

Because quantum angular momentum is defined through L² eigenvalues: L²=l(l+1)ħ². Taking the square root yields |L|=√(l(l+1))ħ, which is what the calculator reports.

4) How many ml values exist for a given l?

There are 2l+1 allowed ml values, from −l to +l. This count also equals the number of orbitals in that subshell before considering electron spin.

5) What is the difference between subshell letters and term letters?

Lowercase letters (s, p, d, f…) map to single-electron l values. Uppercase letters (S, P, D, F…) map to total orbital angular momentum L in LS coupling. They are related ideas but not interchangeable.

6) Can I find l from a measured |L| value?

Yes. Enter |L| in ħ or J·s. The tool solves l(l+1)=(|L|/ħ)² to estimate l and also shows the nearest integer, which is useful when your model requires integer l.

Tip: Run a calculation first to enable the CSV and PDF buttons.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.