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Bonds form and break on their own
Atoms compete for partners, so one bond can form while another breaks. Reactions happen when the physics allows them.
Molecule sandbox · Windows · v0.5.0
Chemistry that isn’t scripted.
Valence is a sandbox for building molecules out of atoms. Drop them in, drag them, shoot them, heat them up, and watch bonds form and break on their own. Nothing is scripted.
Early access is by email for now. There is no public download yet.
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| Water | Valence 0.5.0 | Measured |
|---|---|---|
| Angle | 105.0° | 104.5° |
| O–H | 1.003 Å | 0.958 Å +4.7 % |
| Charge on O | −0.55 e | computed |
Drawn live at the shape Valence 0.5.0 computes. No file in the app describes this molecule.
How it works
Every atom has a valence. That’s the whole idea.
Valence is the number of bonds an atom can make. In the sandbox, atoms compete for partners, and molecules are simply what that competition settles into.
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Shapes aren’t looked up
Water bends and methane turns tetrahedral because of the electrons around each atom, not because a table says so.
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Every number is labelled
Each result shows the model behind it and how far it is from measurement, including where it’s wrong.
What you can do
A box of atoms, and your hands in it.
Some of what happens in Valence 0.5.0.
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Place, drag and shoot atoms
Fire an atom into a molecule and see what the collision does.
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Build molecules atom by atom
Ethane and propane assemble one hydrogen at a time. Methane refuses a fifth.
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Turn up the heat
An oxygen beside an H₂ makes water when you heat it.
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Make ions
Select an atom and press + or −. Charged oxygen grabs a third hydrogen: H₃O⁺.
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Save and pick up exactly where you left off
A reopened scene continues the very same run.
Measured, not assumed
Checked against real molecules, misses included.
2.5%
average bond-length error against measured molecules
1,414
automated tests passing
0
molecules or reactions written into the code
It still gets some chemistry wrong, and says so. See the numbers and the known limits
Also in 0.5.0
Zoom from a drop of liquid down to a quark.
Valence started as a five-scale lab, and 0.5.0 still ships all five. New work goes into the molecule sandbox; the other scales stay as they are.
Scenes below are drawn live in your browser, not captured from the app.
Bulk matter
Liquids and gases as atoms in motion. This box is a real simulation running in your browser.
Molecules in development
The sandbox: atoms competing for partners.
Atom
Electrons as clouds of probability, never as balls on orbits.
Nucleus
Six protons and six neutrons: the heart of a carbon atom.
Quarks
Inside one proton: three quarks bound by the strong force.
Where it’s going
One focus: chemistry that behaves.
A sandbox where everyday chemistry comes out right. Direction, not a schedule.
Now
0.5.0 on Windows
The molecule sandbox, where bonds form and break on their own.
In development
A sharper molecular mode
An optional GPU mode that, in tests, cut the average bond-length error from 2.5 % to 0.71 %.
EXPERIMENTAL not switched on yet
Next research
Reactions that hold up
Fixing the reactions it gets wrong today, and checking the hard cases against reference calculations.
Who’s building it
One founder, and Claude.
Valence is built by Arda Yıldız, with Claude (Anthropic’s model, in Claude Code) as the main engineer. Every change is planned first and measured before it stays.
- 290
- commits, 8–27 September 2026
- 1,414
- automated tests passing
Get involved
Try it early. Tell us where it’s wrong.
Early-access builds go out by email. Spotted something wrong? Tell us.
All of these go to hello@thevalenceapp.com, read by Arda Yıldız.