Why Atoms Are Stable

The uncertainty principle sets the size of atoms

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Confining an electron raises its kinetic energy (uncertainty principle).
• Balancing that against attraction gives the Bohr radius, 0.053 nm, and −13.6 eV.
• Atomic size scales like 1/(electron mass): quantum mechanics is why matter is stable.

Steps

1. A classical disaster
2. Find the size of hydrogen
3. The balance point
4. Heavier electrons
5. Hydrogen’s ultraviolet line
6. Why matter has volume