Filling Order

Building the table element by element

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Electrons fill subshells in energy order: 1s 2s 2p 3s 3p 4s 3d 4p …
• Elements with the same outer configuration form chemical families.
• Row lengths 2, 8, 8, 18, 18, 32, 32 follow from subshell capacities.

Steps

1. Adding electrons one by one
2. Period lengths
3. The table builds itself
4. Unpaired electrons
5. Name that element
6. Chromium breaks the rule
7. Where does the table end?