Explore the Atom Builder
Build atoms from protons, neutrons and electrons and see the element, isotope and charge. Free, no signup, runs in your browser.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
See it in action
The Atom Builder with sample data entered and the result showing.
What is the Atom Builder?
Build atoms from protons, neutrons and electrons and see the element, isotope and charge. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Understanding protons, neutrons and electrons explains isotopes in carbon dating, ions in batteries and body fluids, and why elements behave differently.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
The number of protons (atomic number) decides which element it is.
Changing neutrons makes a different isotope of the same element.
Changing electrons makes an ion: more electrons gives a negative charge, fewer gives positive.
Build carbon-12, then carbon-14.
Remove an electron to make a cation.
Add neutrons and watch the mass number change.
Used for
Pick one to see how it fits.
Atomic & Quantum learners
Advanced high-school and university students in chemistry and physics, and curious learners who want to see how the atomic world behaves.
Try it freeTeachers
For teachers: project the Atom Builder (Isotopes & Ions) on the board, let students predict the result, then run it together and test this: Remove an electron to make a cation. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
What is the difference between an isotope and an ion?
Isotopes have the same protons but different neutrons. Ions have the same protons but a different number of electrons, so they carry a charge.
How do you find the mass number?
Add the protons and neutrons in the nucleus. Electrons are so light they are ignored.
Is the Atom Builder (Isotopes & Ions) free to use?
Yes. The Atom Builder (Isotopes & Ions) is free, needs no signup or download and runs in your web browser. It is part of the Atomic & Quantum group of AZRS simulations.
Does the Atom Builder (Isotopes & Ions) work on a phone or tablet?
Yes. The Atom Builder (Isotopes & Ions) takes touch input as well as mouse input, so you can use its 1 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Atom Builder?
1. In the Atom Builder (Isotopes & Ions), use the controls to change Electron model. The simulation reacts instantly. 2. In the Atom Builder (Isotopes & Ions), pick an option such as Shells (rings), Cloud to switch modes or load an example. 3. In the Atom Builder (Isotopes & Ions), press "+ Proton", "+ Neutron", "+ Electron", "− Proton" to start, reset or change what is happening. 4. Start with this experiment: Build carbon-12, then carbon-14. Drag any glowing handle, object or slider with your mouse or finger and the Atom Builder (Isotopes & Ions) responds in real time. 5. Change one setting at a time and watch which readout moves, then compare it with this idea: The number of protons (atomic number) decides which element it is.
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Try the Atom Builder now
Build atoms from protons, neutrons and electrons and see the element, isotope and charge. Free to use.
Try it free