Science quiz
Which period? Sort the elements by row
The periodic table has seven rows, called periods. An element appears and you click the period it belongs to.
- Format
- Sort into groups
- Items
- 30 to sort
- Limit
- 2:30
- Level
- Hard
- Checked
- 2026.10.03
A fresh 30 of the 118 each time. Today's first round is the same for everyone.
- Items
- 30
- Groups
- 7
- Time limit
- 2:30
- A miss
- 2 tries, then the answer is shown
- Each element appears in turn. Click its period, or press its number.
- The groups never move, so the number keys are quick.
- Skip (0) sends a prompt to the back of the queue.
- Pause whenever you like (Esc). The board hides while the clock is stopped.
Click the period each element belongs to. The groups appear when you start.
About this quiz
A period is a row of the table. An element's period is the number of electron shells its atoms use, so the rows get longer as the shells get roomier: 2, 8, 8, 18, 18, 32 and 32 elements.
- The lanthanides belong to period 6 and the actinides to period 7, although they are drawn below the table.
- Period 1 has only hydrogen and helium.
- Press 1 to 7 to answer from the keyboard.
Sources
- [1]PubChem, National Institutes of Health. Periodic Table of Elements.
Last checked October 3, 2026
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