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Electron configuration lab

Fill the orbitals yourself and watch the three rules bite.

SchoolLive

Scientific learning path

  1. 01UnderstandLive
  2. 02ExploreLive
  3. 03ExperimentLive
  4. 04ObserveLive
  5. 05ExplainLive
  6. 06ApplyLive
  7. 07TestBuilding
Explanation mode
1s
2s
2p
3s
Spin to place

0 of 6 electrons placed

Description of this simulation

Carbon has 6 electrons. No electrons have been placed yet.

CCarbon
Your configuration
No electrons placed yet.
The real configuration
[He] 2s2 2p2
What the Aufbau rule predicts
1s2 2s2 2p2

What the rules say

No electrons placed yet.

Where reality departs from the rule

Here the measured ground state is exactly what the Aufbau order predicts.

The three rules

Aufbau principle
Electrons fill the lowest-energy orbital that still has room.
Pauli exclusion principle
No orbital holds more than two electrons, and those two must have opposite spins.
Hund’s rule
Within a subshell, electrons occupy separate orbitals singly before any orbital takes a second.
See what these orbitals look like

What this model shows — and what it simplifies

Educational Model

Boxes and arrows are a bookkeeping device for which subshell an electron occupies and which way its spin points.

Where do we see this in real life?

Everything the periodic table does follows from these boxes. A half-filled or filled subshell is unusually stable, which is why chromium and copper break the filling order, why manganese has the oxidation states it does, and why the noble gases do almost nothing at all.