CHEMISODE

Atom Builder

All simulations
Particle tray Drag, or tap then tap a target
No particle selected
Protons0
Neutrons0
Electrons0
BOHR SHELL MODEL

Build the atom

Elements 1–20 · shells 2, 8, 8, 2
4th shell · 2
3rd shell · 8
2nd shell · 8
1st shell · 2
NUCLEUS
K0 / 2
L0 / 8
M0 / 8
N0 / 2
SELECT AN ELEMENT

Periodic table

Basic mode: elements 1–20 can be loaded. Information buttons remain available for all elements.

s-block p-block d-block f-block

Select an element to load it into the builder. Use the small i button on a tile to view current physical-property and isotope information from PubChem.
PUBCHEM ELEMENT INFORMATION

Hydrogen

Loading key physical properties and isotope information…

Loading current information from PubChem…
3D ORBITAL VIEWER

All occupied orbitals

The current electron configuration is shown as overlapping probability clouds.

Drag to rotate · scroll or pinch to zoom · double-click/tap an orbital to isolate it Colours show opposite wavefunction phase, not charge.
QUICK GUIDE

How to use Atom Builder

  1. Choose a level. Basic uses four electron shells; Advanced uses subshells, orbital boxes, spin and probability-cloud shapes.
  2. Add particles. Drag a particle from the tray, or tap it and then tap the nucleus, shell or orbital.
  3. Remove a particle. Tap any particle already placed in the model.
  4. Select or investigate an element. Open the element tile in the top-left. Select a periodic-table tile to load the atom, use its small i button for PubChem information, or press Info beside Check build to investigate the element identified by your current proton count.
  5. Explore orbital clouds. In Advanced mode, select a subshell row or orbital box to view its qualitative s, p, d or f probability-cloud shape. Toggle several orbital buttons to display multiple orbitals together. Use the i button beside the orbital-cloud heading to open every occupied orbital in one rotatable viewer.
  6. Check your work. The checker tests particle identity, shell capacity and ground-state electron arrangement.

Chromebook and touch support: both standard drag-and-drop and tap-to-place are included.
DATA & MODEL NOTES

Sources and conventions

Element identity. Atomic number, element names and symbols follow IUPAC. Representative isotope choices are used only when an element is loaded; the live mass number is always calculated as protons + neutrons.

Periodic-table information buttons. The small i buttons request current property and isotope summaries from PubChem PUG View. The builder itself remains usable if the internet or PubChem service is unavailable.

Electron configurations. Neutral ground-state configurations through uranium follow the NIST electronic-configuration reference. Superheavy-element configurations are labelled as predicted educational configurations where direct experimental assignments are limited.

Basic shell model. The 2,8,8,2 model is an intentional Years 7–10 simplification for elements up to calcium. The Advanced view should be used when subshells and orbitals matter.

Spin and filling. The checker applies the Pauli exclusion principle, Hund’s rule and the standard Aufbau energy order, while retaining recognised neutral-atom exceptions in the reference configuration.

Open IUPAC periodic table Open NIST configurations Open PubChem periodic table