Aufbau, Hund and Pauli

Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 25 of 45.

Aufbau: fill the lowest subshell first, 1s, 2s, 2p, 3s, 3p, 4s, 3d. Pauli: at most 2 electrons a box, spinning opposite ways, ↑↓.

Hund: in p or d, one electron in each box first, all pointing the same way, before any pair.

Carbon's 2p electrons wrongly paired in one box, ringed in red

This breaks Hund's rule

Carbon done right: one up arrow in each of two 2p boxes.

Carbon's boxes drawn right: two single up arrows in 2p

Carbon, following all three rules

Challenge

A classmate drew oxygen, with 8 electrons, like this. Draw oxygen's boxes correctly.

Oxygen drawn wrong: two pairs in 2p and an empty third box, ringed in red

Oxygen, drawn wrong

Try it yourself

Orbital boxesFill the electrons of O (oxygen)

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Atomic Structure

1Matter and Atoms

4Electron Arrangement

7Practice Problems

2Models of the Atom

5The Periodic Table

3Inside the Atom

6Periodic Trends