Periodically

Solve all three lines by placing the correct elements (e.g., Na, H, O) into the boxes next to each clue.

• Drag a tile from the Lab to a box, or tap a tile then tap a box.
• Tap a placed tile’s × to send it back to the Lab.
• Use a clue’s 💡 for a hint (costs 1 attempt).
• If the Lab is hidden, tap the 🧪 Lab button on the lower-left to show it.

Tiles light up on submit:
Green = right element & spot • Yellow = right element, wrong spot • Gray = not in that answer.