Build an atom, then spin it around.
Pick an element or add particles one at a time. Drag anywhere on the model to rotate it, scroll or pinch to zoom, and hover a particle to see what it is.
Everything responds to a click or a drag.
No menus to dig through — the whole model is the interface.
Pick a starting atom
Choose an element from the dropdown or click a tile in the mini periodic grid — the model rebuilds itself instantly with the right shells filled.
Spin and zoom the model
Click and drag anywhere on the stage to rotate the atom in 3D, and use the + / − buttons or your scroll wheel to zoom into the nucleus.
Add or remove particles
Use the proton, neutron and electron steppers to turn an element into an isotope or an ion and watch the shells and charge badge update live.
Hover to identify a particle
Hover any orbiting electron or any particle packed into the nucleus to see exactly what it is and where it sits in the structure.
What you're actually looking at.
The model is drawn to make three real physical facts easy to see, not just decorative motion.
The nucleus
The tightly packed core in the middle holds essentially all of the atom's mass. Protons carry a positive charge; neutrons carry none. Together they set the mass number.
The shells
Each ring is a fixed energy level. Electrons (teal) always fill the innermost open shell first, which is why the model fills from the center outward as you add electrons.
The outer ring
The electrons in the last, outermost shell are the ones involved in bonding. The readout panel highlights this shell's count separately for exactly that reason.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is the Bohr model of the atom?+
The Bohr model shows electrons traveling in fixed circular shells around a central nucleus, each shell holding a maximum number of electrons. It's a simplified picture — real electrons occupy fuzzy probability clouds called orbitals — but it's the clearest way to see shell structure and electron configuration at a glance.
How do you find the number of protons, neutrons and electrons in an atom?+
The number of protons equals the atomic number and defines the element. In a neutral atom, the number of electrons equals the number of protons. The number of neutrons is the mass number minus the atomic number, so heavier isotopes of the same element simply carry more neutrons.
How many electrons fit in each shell?+
The first shell holds up to 2 electrons, the second and third shells hold up to 8 each in the simple filling order used for the first 20 elements, and the fourth shell continues filling once the third holds its outer 8. Electrons always fill the lowest available shell first.
What happens to an atom when it becomes an ion?+
An atom becomes an ion when it gains or loses electrons while the proton count stays the same. Losing electrons leaves more protons than electrons, giving a positive charge; gaining electrons gives a negative charge. The identity of the element never changes because that depends only on the proton count.
What is an isotope?+
Isotopes are atoms of the same element — same number of protons — with different numbers of neutrons, which changes the mass number but not the chemical identity or charge. Carbon-12 and carbon-14 are both carbon because both have 6 protons; they differ only in neutron count.
Why are valence electrons important?+
Valence electrons are the electrons in the outermost shell, and they're almost entirely responsible for how an atom bonds with others. Atoms tend to gain, lose, or share valence electrons to reach a full outer shell, which is the basis of nearly all chemical bonding.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you build or click is uploaded, logged, or sent to any server. No account, no sign-up, no limits.