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Foundation Chemistry

Structure of Atom: Bohr Model & Quantum Numbers

Dr. Aarzoo Saini
August 2026
6 min read

Master principal, azimuthal, magnetic, and spin quantum numbers alongside orbital electronic configuration rules.

Structure of Atom lays the physical framework for understanding chemical bonding and periodic behavior. Mastering subatomic particles, electromagnetic radiation, and quantum mechanics is fundamental for Class 11 Chemistry.

Bohr's Model & Line Spectra: Postulates quantized electron orbits with angular momentum L = nh / 2pi. Energy of electron En = -13.6 Z^2 / n^2 eV. Rydberg formula calculates wavenumber for hydrogen spectral lines (Lyman, Balmer, Paschen, Brackett, Pfund).

Dual Nature & Quantum Principles: de Broglie wavelength lambda = h / mv. Heisenberg Uncertainty Principle: Delta x * Delta p >= h / 4pi, proving that precise electron trajectories cannot be determined.

Quantum Numbers & Electronic Configuration: Four quantum numbers define orbital state: Principal (n), Azimuthal (l = 0 to n-1), Magnetic (m = -l to +l), and Spin (s = +1/2, -1/2). Electronic filling follows Aufbau principle, Pauli exclusion principle, and Hund's rule of maximum multiplicity. Dr. Aarzoo Saini trains students in orbital filling rules at We-Gyaan Classes.

Key Takeaways for Students

  • Calculate spectral line wavelengths using Rydberg equation.
  • Apply de Broglie wavelength and Heisenberg uncertainty formulas.
  • Determine orbital designations and electron capacities from quantum numbers.
  • Write ground state electronic configurations following Aufbau, Pauli, and Hund rules.
Dr. Aarzoo Saini

Authored by Dr. Aarzoo Saini

Founder & Lead Educator at We-Gyaan Classes Roorkee, with over 20 years of teaching excellence in Science and Chemistry for Board Exams, NEET, JEE, and CUET.

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