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Why does quantum mechanics describe atoms better than classical mechanics?

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A diagram of a cylindrical vessel containing gas, with a movable piston held down by a weight. Countless small dots beneath the piston represent gas particles in rapid, random motion, illustrating Bernoulli's model of gas pressure. — physics As conceived by Daniel Bernoulli in *Hydrodynamica* (1738), gases consist of numerous particles in rapid random motion. He assumed that the pressure of a gas is produced by the direct impact of the particles on the walls of the container.

Quantum mechanics describes atoms more accurately than classical mechanics because classical physics fails to account for the stability and discrete energy states of atomic systems.12

Under classical electromagnetic theory, a charged particle moving on a curved path—such as an electron orbiting a nucleus—should continuously emit radiation, causing it to lose energy and spiral into the nucleus. Quantum mechanics resolves this by treating electrons as standing waves constrained to specific, discrete energy levels. Atoms only emit or absorb radiation when electrons undergo discontinuous transitions, or "quantum jumps," between these allowed states.314

Furthermore, quantum theory replaces the deterministic nature of classical physics with the uncertainty principle, which recognizes that one cannot simultaneously measure a particle's position and momentum with absolute precision. While classical mechanics cannot explain the structure of multielectron atoms or the fine details of spectroscopy, quantum mechanics provides a robust framework that has been experimentally verified with extraordinary precision.1532