Textbooks

1. Griffiths, D. J., & Schroeter, D. F. (2018). Introduction to Quantum Mechanics (3rd ed.). Cambridge University Press.
   (Chapter 4: Full derivation in spherical coordinates; energy (E_n) independent of (l, m))

2. Shankar, R. (2012). Principles of Quantum Mechanics (2nd ed.). Springer.
   (Chapter 12: Operator methods, angular momentum separation)

3. Messiah, A. (1999). Quantum Mechanics (Vol. 1, Dover ed.). Dover Publications.
   (Chapter XII: Exact solutions, relativistic corrections)

4. Sakurai, J. J., & Napolitano, J. (2020). Modern Quantum Mechanics (3rd ed.). Cambridge University Press.
   (Chapter 4: Central potentials, Runge–Lenz vector)

5. OpenStax. (2016). University Physics Volume 3. OpenStax.
   https://openstax.org/details/books/university-physics-volume-3
   (Chapter 8: Introductory orbitals, Bohr model comparison)

6. Ghatak, A. K., & Lokanathan, S. (2004). Quantum Mechanics: Theory and Applications (5th ed.). Macmillan Publishers India Limited.
   (Chapter 10: spherically symmetric potentials)

Online Resources

1. Wikipedia contributors. (2026). Hydrogen atom.
   https://en.wikipedia.org/wiki/Hydrogen_atom
   (Bohr model to Schrödinger equation; quantum numbers (n, l, m, s); fine structure)

2. Physics LibreTexts. (2025). 8.2: The Hydrogen Atom.
   https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/.../8.2:_The_Hydrogen_Atom
   (Wavefunctions and probability densities)

3. Zwiebach, B. (2013). Quantum Physics I (MIT OpenCourseWare 8.04).
   https://ocw.mit.edu/courses/8-04-quantum-physics-i-spring-2013/
   (Lectures on radial equation and degeneracy)

4. Khan Academy. (2025). The quantum mechanical model of the atom.
   https://www.khanacademy.org/science/physical-chemistry-essentials/.../quantum-mechanical-model
   (Introductory explanation of atomic orbitals)