Quiz: Electron Configuration Calculator

Practice writing electron configurations for randomly generated elements and ions, then check your answer instantly against the worked solution.

📝 Electron Configuration Quiz
Your Answer
Result
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Your Answer
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Correct Answer
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Worked Solution
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Score: 0 / 0

📝 What is the Electron Configuration Quiz?

The Electron Configuration Quiz is an interactive practice tool that generates random elements and ions for you to write ground-state electron configurations for, then checks your answer instantly and shows the complete worked solution. Unlike a lookup calculator, this quiz hides the answer until you attempt it yourself, making it a genuine practice and self-testing tool rather than a reference.

The quiz covers two question types. Full Configuration mode asks you to write out the entire electron configuration for a randomly chosen neutral atom (atomic numbers 1 through 36, hydrogen through krypton) or a common monatomic ion (like Na+, Cl-, or O2-), testing your ability to apply the Aufbau principle and n+l filling order from memory, including recognising the chromium and copper exceptions. Subshell Count mode asks a more targeted question, how many electrons occupy one specific subshell of a given element, which builds faster recall of individual subshell capacities.

This differs sharply from the companion Electron Configuration Calculator, which is a direct lookup tool that simply returns the answer for any element you type in. That calculator is for checking or referencing a configuration you already need; this quiz is for building the skill of writing configurations yourself, with a running score tracker so you can measure your progress across a practice session.

Each question is randomly generated, giving unlimited variety for exam preparation, homework review, or self-study. After every attempt, right or wrong, the full worked solution is shown, so incorrect answers become learning opportunities rather than dead ends.

📐 Rule Being Tested

Fill order by increasing (n + l), lowest n first on ties
n = principal quantum number (shell number: 1, 2, 3, ...)
l = angular momentum quantum number (s = 0, p = 1, d = 2, f = 3)
Order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, ...
Ions: electron count = Z − charge (cations lose electrons, anions gain electrons)

📖 How to Use This Quiz

Steps to build electron configuration fluency

1
Pick a quiz mode - choose Full Configuration to practise writing entire electron configurations, or Subshell Count to practise counting electrons in one subshell.
2
Read the randomly generated question - the quiz shows a randomly chosen element or common ion for you to work out.
3
Work out your answer - apply the Aufbau principle and n+l filling order (or the known Aufbau exceptions) to determine the correct configuration or subshell count.
4
Enter and check your answer - type your answer and click Check Answer for instant feedback and a full worked solution.
5
Try another question - click New Question to generate a fresh random problem and keep building recall speed.

💡 Example Problems

Example 1 — Nitrogen (Z = 7)

Write the full ground-state electron configuration for N (Z = 7).

1
Fill 1s, then 2s, then 2p, placing 7 electrons total in order.
2
1s takes 2, 2s takes 2, leaving 3 for 2p.
Answer = 1s2 2s2 2p3
Try this example →

Example 2 — Chlorine (Z = 17)

Write the full ground-state electron configuration for Cl (Z = 17).

1
Fill 1s2 2s2 2p6 3s2 (12 electrons so far), which uses up the 1s, 2s, 2p, and 3s subshells.
2
17 - 12 = 5 electrons remain, all going into 3p.
Answer = 1s2 2s2 2p6 3s2 3p5
Try this example →

Example 3 — Chromium (Z = 24, Aufbau exception)

Write the full ground-state electron configuration for Cr (Z = 24).

1
The naive fill order gives 4s2 3d4, but chromium is a known exception.
2
A half-filled 3d5 subshell is more stable, so one 4s electron moves to 3d.
Answer = 1s2 2s2 2p6 3s2 3p6 3d5 4s1
Try this example →

Example 4 — Subshell count for chlorine's 3p

How many electrons are in the 3p subshell of Cl (Z = 17)?

1
Chlorine's full configuration is 1s2 2s2 2p6 3s2 3p5.
2
Read off the electron count listed directly after 3p.
Answer = 5
Try this example →

❓ Frequently Asked Questions

How is this quiz different from the Electron Configuration Calculator?+
The Electron Configuration Calculator is a direct lookup tool, you type an element and instantly get its configuration. This quiz is the opposite: it hides the answer and asks you to write the configuration yourself for a randomly generated element or ion, then checks whether your answer is correct and shows the worked solution.
How do I format my answer for the Full Configuration mode?+
Write each subshell followed by its electron count with no space between the subshell and number, separated by spaces between subshells, for example 1s2 2s2 2p6 3s2 3p5. The order you list the subshells in does not matter, the checker matches subshell-electron pairs regardless of sequence.
What elements does this quiz cover?+
The quiz draws neutral atoms from atomic numbers 1 through 36 (hydrogen through krypton), plus a curated set of common monatomic ions including Na+, Mg2+, Al3+, K+, Ca2+, F-, Cl-, O2-, S2-, and N3-, which are the ions most frequently tested in introductory chemistry courses.
How does the quiz handle ions?+
For an ion question, the number of electrons differs from the atomic number by the ion's charge: a cation like Na+ has one fewer electron than sodium's atomic number (10 electrons instead of 11), while an anion like Cl- has one more electron than chlorine's atomic number (18 electrons instead of 17). The quiz builds the configuration from the correct electron count, not the atomic number.
Does the quiz include the chromium and copper Aufbau exceptions?+
Yes. Chromium (Z = 24) and copper (Z = 29) are both included in the quiz's element range, and their correct answers use the true exception configuration (4s1 3d5 for chromium, 4s1 3d10 for copper) rather than the naive predicted configuration, so you can practise recognising these well-known exceptions.
What does the Subshell Electron Count mode ask?+
This mode picks a random element and a random subshell that actually has electrons in that element's ground state, then asks how many electrons occupy just that one subshell. For example, how many electrons are in the 3p subshell of chlorine, answer 5. It is a faster way to practise recalling individual subshell capacities and fill patterns.
Is my score saved between visits?+
No. The running score counter (correct answers out of total questions attempted) only persists for your current browser session on this page. Refreshing or leaving the page resets the counter to zero, so it is intended as in-session practice feedback, not a permanent record.
What happens if I get an answer wrong?+
The quiz marks your answer as incorrect, shows you the correct configuration or subshell count, and displays a short worked solution explaining how the correct answer was derived. You can then click New Question to try a fresh, randomly generated problem.
Why does my Full Configuration answer need a specific electron count per subshell, not superscripts?+
The answer checker reads plain digits (like 2p6) rather than superscript characters (like 2p⁶), since superscripts are difficult to type on a standard keyboard. Type the electron count as a normal digit immediately after the subshell letters, and the checker will accept it correctly.
Can I use this quiz to prepare for a chemistry exam?+
Yes. Writing ground-state electron configurations from memory, including recognising the handful of common Aufbau exceptions, is a frequently tested skill in general chemistry courses. Working through randomly generated questions in both modes, full configuration and subshell counting, builds the recall speed and accuracy needed for timed exams.
Tags: Electron Configuration Quiz Aufbau Principle Practice Electron Configuration Practice Chemistry Quiz Subshell Electron Count Quiz Calculator Free Online

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How is this quiz different from the Electron Configuration Calculator?

The Electron Configuration Calculator is a direct lookup tool, you type an element and instantly get its configuration. This quiz is the opposite: it hides the answer and asks you to write the configuration yourself for a randomly generated element or ion, then checks whether your answer is correct and shows the worked solution.

How do I format my answer for the Full Configuration mode?

Write each subshell followed by its electron count with no space between the subshell and number, separated by spaces between subshells, for example 1s2 2s2 2p6 3s2 3p5. The order you list the subshells in does not matter, the checker matches subshell-electron pairs regardless of sequence.

What elements does this quiz cover?

The quiz draws neutral atoms from atomic numbers 1 through 36 (hydrogen through krypton), plus a curated set of common monatomic ions including Na+, Mg2+, Al3+, K+, Ca2+, F-, Cl-, O2-, S2-, and N3-, which are the ions most frequently tested in introductory chemistry courses.

How does the quiz handle ions?

For an ion question, the number of electrons differs from the atomic number by the ion's charge: a cation like Na+ has one fewer electron than sodium's atomic number (10 electrons instead of 11), while an anion like Cl- has one more electron than chlorine's atomic number (18 electrons instead of 17). The quiz builds the configuration from the correct electron count, not the atomic number.

Does the quiz include the chromium and copper Aufbau exceptions?

Yes. Chromium (Z = 24) and copper (Z = 29) are both included in the quiz's element range, and their correct answers use the true exception configuration (4s1 3d5 for chromium, 4s1 3d10 for copper) rather than the naive predicted configuration, so you can practise recognising these well-known exceptions.

What does the Subshell Electron Count mode ask?

This mode picks a random element and a random subshell that actually has electrons in that element's ground state, then asks how many electrons occupy just that one subshell. For example, how many electrons are in the 3p subshell of chlorine, answer 5. It is a faster way to practise recalling individual subshell capacities and fill patterns.

Is my score saved between visits?

No. The running score counter (correct answers out of total questions attempted) only persists for your current browser session on this page. Refreshing or leaving the page resets the counter to zero, so it is intended as in-session practice feedback, not a permanent record.

What happens if I get an answer wrong?

The quiz marks your answer as incorrect, shows you the correct configuration or subshell count, and displays a short worked solution explaining how the correct answer was derived. You can then click New Question to try a fresh, randomly generated problem.

Why does my Full Configuration answer need a specific electron count per subshell, not superscripts?

The answer checker reads plain digits (like 2p6) rather than superscript characters (like 2p⁶), since superscripts are difficult to type on a standard keyboard. Type the electron count as a normal digit immediately after the subshell letters, and the checker will accept it correctly.

Can I use this quiz to prepare for a chemistry exam?

Yes. Writing ground-state electron configurations from memory, including recognising the handful of common Aufbau exceptions, is a frequently tested skill in general chemistry courses. Working through randomly generated questions in both modes, full configuration and subshell counting, builds the recall speed and accuracy needed for timed exams.

📌 Quick Tips

💡This is a practice quiz, not a lookup tool. If you just need to look up one element's configuration instantly, use the standalone Electron Configuration Calculator instead.
💡Type your full configuration answer with spaces between subshells, e.g. 1s2 2s2 2p6, but the order you list subshells in does not matter, only the subshell-electron pairs need to match.
💡About 30 percent of Full Configuration questions use a common ion instead of a neutral atom, remember that an ion's electron count differs from its atomic number by its charge.
💡Elements 24 (chromium) and 29 (copper) are the two Aufbau exceptions included in this quiz's element range (1-36), watch for them specifically to test your knowledge of exceptions.
💡The Subshell Electron Count mode only ever asks about subshells that actually contain at least one electron in that element's ground state, so the answer is never zero.