Chemistry you watch emerge.
Aufbau keeps no library of molecules and no list of reactions. Give it atoms and it computes how they bond, plans a multistep synthesis, and — on a single energy principle — carries all the way to the nucleus.
It stores nothing it can compute.
Most learning software shows you an answer pulled from a database. Aufbau holds none. A structure appears because it minimizes an energy score under each atom's valence; a reaction proceeds because a search finds a downhill path to the target. Behavior you watch emerge from a principle is understood more deeply than behavior you are simply shown.
Don't look it up. Derive it.— The whole idea, in four words
From a pile of atoms to a computed route.
Atoms in.
Drop in the elements — no structure, no bonds. Just atoms and the principles every introductory course already teaches: valence, electronegativity, energy.
Energy decides.
The engine scores every possible bonding arrangement and keeps the one that minimizes it. Covalent, ionic, metallic, aromatic — all outcomes of one comparison, not stored categories.
Structure emerges.
Molecules assemble, multistep syntheses plan themselves, and the same energy rule reaches into the nucleus. Every result traces back to the step that produced it.
From atoms to entanglement — in under two minutes.
The whole story in one take: structure emerges, a synthesis plans itself, and the same energy principle reaches the nucleus — then the app computes the quantum layer beneath the chemistry, all the way to a molecular qubit and an entangled pair.
Six things you can watch it compute.
Watch molecules build from atoms
Bonds form because they minimize energy under each atom's valence — the bent water molecule, the tetrahedral carbon of methane, the alternating ring of benzene. Nothing is looked up.
See the delocalized cloud
The Hückel rule, applied uniformly, certifies aromatic rings from benzene to the macrocycle at the heart of heme and chlorophyll — metal center and coordinate bonds and all.
Plan a synthesis backwards
The engine proposes a strategic disconnection and validates it against the same forward model that would run the synthesis — keeping only cuts it can itself reverse. No transform library.
Power a reaction with a reactor
A thorium fission source drives a water-splitting cycle, and a live ledger measures the clean hydrogen it makes against the gasoline it replaces — every number computed from the engine's own physics.
Test your own reactions
Type a formula or paste a SMILES structure — Vitamin C, aspirin, your own molecule — set the temperature, and get the engine's honest verdict with the energy change. Rotate any molecule in 3-D (real geometry, π clouds), ask it to work out a retrosynthesis down to buyable building blocks, or send the mixture to the live reactor to watch it play out. Save what works to your own library and name it; keep the near-misses to refine later.
One engine — all the way to the nucleus.
Chemical bonding and nuclear stability are usually separate subjects, on separate energy scales, with separate software. Aufbau asks both the same question: does this rearrangement release energy?
Ask it of electrons and you get chemistry. Ask it of nuclei and you get decay, fission, fusion — and the alchemist's route from mercury to gold, forbidden as a shortcut and forced into its real two-step path by the arithmetic of binding energy.
The honest answers.
Is this a real chemistry engine or just animations?
Real. Structures and reactions are computed from an interpretable bonding model and the semi-empirical mass formula — not retrieved from a database. You can trace any result down to the rule that produced it, including where a simple model reaches its limits.
What platform does it run on?
macOS. It is a native app; a Mac App Store release is in progress. This page will carry the download link the day it goes live.
Who is it for?
Undergraduate and advanced high-school chemistry — general through introductory organic — plus an optional nuclear-chemistry module. For instructors who want to show why, and students who want to see it.
Does it collect any data?
No. Aufbau runs entirely on your device, collects nothing, and makes no network connections. Details on the Privacy page.
Can it really turn mercury into gold?
In the model, yes — the physics is genuine and the route is forced by binding energy. In reality it needs a reactor and a rare isotope, so the gold would cost far more than mining it. Physics: yes. Economics: no.
Chemistry is just the surface.
Beneath the bonds, Aufbau computes the electronic structure itself — molecular orbitals, unpaired spins, a molecular qubit, an entangled pair. Thirty seconds of the layer underneath.