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Main positions:Director, High Performance Computing Platform, PKU
Degree:Doctoral degree
Status:Employed
School/Department:Institute of Theoretical Physics

Lei Yian

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Education Level: Postgraduate (Doctoral)

Administrative Position: Associate Professor

Alma Mater: Peking University

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The Complete Picture of the Classical Atomic Model
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I. Why Doesn't the Planetary Model Work?

After Rutherford discovered the atomic nucleus in 1911, people naturally drew an analogy to the solar system. However, classical electrodynamics immediately pointed out a fatal flaw:

  • Accelerated charges must radiate electromagnetic waves.

  • Circular motion involves continuous centripetal acceleration → electrons continuously lose energy → collapse into the nucleus in approximately 10^-11 seconds.

  • More critically, the radiation should form a continuous spectrum, but experiments show atomic spectra are discrete line spectra.

Bohr attempted to patch this with "quantum jumps," but he couldn't explain why the orbital angular momentum of the hydrogen atom's ground state (1s state) is zero—how could a "planet" not rotate?

A deeper issue lies in this:While circular orbital motion generates a varying electric field, the direction of its acceleration rotates constantly, failing to form an effective closed loop for electric-magnetic energy exchange. It acts only as a unidirectional radiation source, not a self-sustaining oscillatory system.

Conclusion: Electrons do not orbit the nucleus; the orbital model is not only unstable but also lacks the physical mechanism to produce intrinsic resonance.

II. Is the Quantum "Stationary State" Truly Stationary?

Quantum mechanics states that the ground state of a hydrogen atom is a "stationary state," with a probability density |ψ|² that does not change with time. Many mistakenly believe electrons are "motionless," but this is a misunderstanding.

  • The wave function itself contains a time-dependent phase: Ψ(r,t) = ψ(r)e^(-iEt/ħ).

  • For s orbitals (e.g., 1s, 2s), while there is no net current, the charge distribution has radial nodes (e.g., the 2s orbital has zero probability at a certain radius).

These nodes imply: Electrons are not stationary but exist in a dynamically balanced standing wave state.

Key Insight:A "stationary state" does not mean the electron is motionless; instead, the system enters a self-consistent oscillatory mode with no net radiation—its internal energy periodically converts between electric and magnetic fields, resulting in zero average radiation.

III. The Real Motion of Atoms: Dominated by Radial Oscillation

Experiments and theories consistently show that the dominant motion of electrons is back-and-forth radial oscillation, not angular orbiting.

  • Zero angular momentum in the ground state: The orbital angular momentum L = 0 for the hydrogen atom's 1s state, ruling out circular motion.

  • s electrons can penetrate the atomic nucleus: Hyperfine interactions prove electrons can "reach" the nucleus, a phenomenon only possible through radial traversal.

  • Radial nodes in excited states: The number of nodes in the wave functions of 2s, 3s, etc., exactly corresponds to the number of nodes in a standing wave.

More importantly, radial oscillation inherently provides the physical basis for electromagnetic resonance:

When the electron approaches the nucleus:

  • Charge distribution concentrates → electric field strengthens, and electric energy (potential energy) reaches a minimum (maximum absolute value).

  • Velocity is maximum → kinetic energy is maximum.

  • The varying electric field generates a strong magnetic field → magnetic energy increases.

When the electron moves away from the nucleus:

  • Electric field weakens → electric energy rises.

  • Velocity decreases → kinetic energy drops.

  • Magnetic field decays → magnetic energy decreases.

🔁 The periodic conversion of electric energy ↔ kinetic energy ↔ magnetic energy constitutes self-sustaining electromagnetic oscillation. It is this oscillation that makes the atom a natural electromagnetic resonator.

This is precisely what the orbital model cannot achieve: While circular motion involves the exchange of kinetic and potential energy, it lacks significant radial electric field changes, making it difficult to excite effective magnetic oscillation and even harder to form a stable standing wave structure.

IV. The Atom as an Electromagnetic Resonator

The core idea is: An atom is not an isolated particle system but an electromagnetic resonator.

  • Radial oscillation of electrons → generates time-varying charge distribution → excites electromagnetic fields.

  • Electromagnetic fields, in turn, constrain electron motion → form a self-consistent feedback loop.

  • Only oscillatory modes with certain eigenfrequencies can persist long-term (satisfying phase matching and boundary conditions).

  • These eigenmodes correspond to energy levels in quantum mechanics (e.g., E_n = -13.6/n² eV).

  • Quantization is not an assumption but a natural result of the resonant cavity—just as a guitar string can only produce specific pitches.

By matching the classical action integral (∮pdr = nh) with resonance conditions, Bohr's energy levels can be derived without introducing wave function collapse.

V. Mass Defect and Energy Conservation

When a free electron combines with a proton to form a hydrogen atom:

  • The total energy of the system decreases by 13.6 eV (binding energy).

  • This energy is radiated away as a photon.

  • According to E = mc², the mass of the hydrogen atom is less than the sum of the masses of the electron and proton—this is the "mass defect."

In the classical picture:

  • Mass defect mainly arises from the reduction in electromagnetic field energy (as positive and negative charges approach, their electric fields cancel out).

  • While the electron's kinetic energy increases, the decrease in potential energy is greater.

  • The total mass is determined by the total energy of the system, not the sum of the rest masses of its components.

This energy conversion process is realized through the reconstruction of the electromagnetic field driven by radial oscillation.

VI. Returning to Reality, Not the Past

This classical atomic model does not seek to negate quantum mechanics but to provide a physically realistic interpretation of it:

Quantum Concept Classical Counterpart
Wave function ψ Complex amplitude of the electromagnetic standing wave
Energy level E_n Energy of the resonant cavity's eigenmode
Probability density Electromagnetic field intensity
Quantization Standing wave requirement under boundary conditions

It explains:

  • Why atoms are stable (resonance locking).

  • Why spectra are discrete (eigenfrequencies).

  • Why s states have no angular momentum (pure radial oscillation).

  • Why mass defect exists (reduction in field energy).

  • Why the orbital model is inherently flawed (inability to produce electric-magnetic energy oscillation and intrinsic resonance).

Conclusion: The Atom as an Electromagnetic Symphony

The atom is neither a cold probability cloud nor an outdated planetary system. It is a dynamic, self-consistent, resonant classical electromagnetic system—electrons undergo radial oscillation in the Coulomb potential, driving the periodic conversion of electric and magnetic energy to form stable electromagnetic standing waves. The system exists stably in the lowest-energy eigenmode and radiates light of specific frequencies.

It is this electromagnetic oscillation, centered on radial motion, that forms the physical basis for the stable existence of atoms and completely negates any classical picture relying on angular orbits.

This model demystifies quantum mechanics, allowing us to reaffirm that the fundamental laws of nature can be intuitively understood.

As one physicist put it:

"If quantum mechanics doesn't make sense to you, it's probably because you haven't found the right classical picture."

Today, we may be standing at the threshold of that picture.