Each element's electrons are placed using the Aufbau principle, Hund's rule (unpaired electrons fill degenerate orbitals before pairing), and the Pauli exclusion principle (max 2 electrons per orbital, opposite spin). Orbital shapes and sizes come from actual hydrogen-like wavefunctions solved for an effective nuclear charge computed with Slater's shielding rules — heavier, more-screened electrons genuinely render as larger, more diffuse clouds.
A schematic Bohr-style map: each ring is a principal shell n, electrons sit on it as small spheres. This is not a literal orbit — real electrons don't circle the nucleus like planets — it's a way to see shell occupancy and spin pairing at a glance.
Each point is a Monte-Carlo sample of |ψ|², so the cloud density you see is the actual electron probability distribution. Point color shows the sign of the wavefunction (phase), which is why some lobes are blue and others coral — and why you can spot radial nodes as gaps between shells of the same orbital.
Select a subshell to see its electrons listed here.
This uses hydrogen-like orbitals with Slater screening, the standard classroom approximation — real multi-electron wavefunctions are correlated and not exactly separable this way. Elements are supported up to Z = 36 (Krypton); f-orbitals aren't included.