Petameter to Bohr Radius

The Bohr radius is the most probable distance between the nucleus and the electron in a ground-state hydrogen atom, approximately 5.292 × 10⁻¹¹ meters.

a₀ = ℏ/(mec α) = 4πε₀ℏ²/(mee²) ≈ 5.29177 × 10⁻¹¹ m, where α is the fine-structure constant.

To convert Bohr radii to meters: multiply by 5.29177210903 × 10⁻¹¹.

Sets the characteristic scale for atomic sizes. Most atoms have radii of 1–3 Bohr radii.

The Bohr radius gives atoms their characteristic size of ~1 Å (10⁻¹⁰ m), explaining why matter has the volume it does.

Confusing Bohr radius with atomic radius — the Bohr radius is specific to hydrogen; other atoms have different sizes.

The Bohr radius tells you 'how big atoms are' — about 0.5 angstroms. It's the atomic analog of a ruler for atomic-scale physics.