Click on the gray path connected to the green nucleus and connect it to the black circle. The number on the nucleus indicates how many electrons you need connected before reaching the end. So when making your path, make sure you connect the nucleus to all electrons!

Click the Play button to watch the nucleus go down the path. If you make a mistake, click the Edit button to remake your path.

HINT: Avoid dark matter boxes as neither the nucleus or electrons can pass through them.