Atomic Orbital Lab

Electrons do not orbit the nucleus like planets. They occupy orbitals — regions where the electron is likely to be found. This lab draws a cross-section through those regions.

Not a path — a probability cloud

The shaded area is not a trajectory. It is where the electron turns up most of the time. The shading is densest where the probability is highest, and there are surfaces where the probability is exactly zero — nodes. An electron never crosses a node; it simply is never found there.

Quantum numbers

• n (shell) — size and energy. Bigger n, bigger cloud.
• l (shape) — 0 = s, 1 = p, 2 = d, 3 = f.
• m (orientation) — how the shape is turned in space.

The nodal rule

The number of radial nodes follows a strict formula: n − l − 1. Check it in the lab:

• 1s: n=1, l=0 → 0 nodes. A plain ball.
• 2p: n=2, l=1 → 0 radial nodes, but a nodal plane through the nucleus, giving two lobes.
• 3d: n=3, l=2 → 0 radial nodes and a four-lobed clover shape.
• 2s: n=2, l=0 → 1 radial node: a ball inside a shell, with a gap between.

Why the periodic table has blocks

Each orbital holds two electrons (one spin up, one spin down). An s subshell has 1 orbital → 2 electrons. p has 3 orbitals → 6. d has 5 → 10. f has 7 → 14. Those numbers are exactly the widths of the blocks in the periodic table: the s-block is 2 columns wide, the p-block 6, the d-block 10. The table’s shape is a direct picture of quantum mechanics.

Try this

• Step through 1s → 2s → 3s and watch radial nodes appear one at a time.
• Jump to 3d and rotate your mental model: four lobes, two nodal planes.
• Raise the contour level — the cloud shrinks toward the densest region, showing that the “edge” of an atom is a choice, not a boundary.

Why it matters

Orbital shapes determine molecular geometry (and therefore every property of every material), the colours of transition metal compounds, how atoms bond, and how lasers and LEDs emit light.