The Atomic theory model which explains that electrons in an atom revolve round quantized energy levels is attributed to

Step 1: Analyze the question The question asks which scientist's atomic model describes electrons revolving around the nucleus in quantized energy levels (fixed orbits or shells).

Step 2: Explain the concept Each scientist is linked to a different idea:

• Becquerel: discovered radioactivity (1896). He did not propose an atomic model.
• Thomson: proposed the "plum pudding" model, with electrons embedded in a positively charged sphere.
• Rutherford: proposed the nuclear model after the gold foil experiment. Electrons orbit a small, dense, positive nucleus, but he did not explain why they don't spiral into it, and he had no quantized levels.
• Bohr (1913): improved on Rutherford's model. Electrons move in fixed, circular orbits (energy levels or shells) with definite, quantized energies. An electron emits or absorbs energy only when it jumps between levels, and this explains line spectra.
• de Broglie: proposed the wave-particle duality of matter (λ = h/mv). This later supported the quantum mechanical model, but it is not the "revolving in quantized levels" model.

Step 3: Solution The key phrase "electrons revolve round quantized energy levels" matches Bohr's postulates:

1. Electrons revolve in stable orbits without radiating energy.
2. Only certain orbits are allowed, where angular momentum is quantized: mvr = nh/2π.
3. Energy is absorbed or emitted when an electron moves between levels: ΔE = hf.

Step 4: Answer The model is attributed to Bohr, which is option B.

Tip: Link each name to a keyword:

• Thomson → plum pudding
• Rutherford → nucleus
• Bohr → energy levels/shells
• de Broglie → matter waves
• Becquerel → radioactivity

Whenever you see "quantized" with "orbits" or "energy levels", think Bohr.