Principal quantum number n labels basic states of a system. Energy states of bound systems are quantized as En∝1/n². Lowest-energy state has n=1, first excited state has n=2
Quantum numbers characterize possible states of quantum systems. Four quantum numbers describe electron states in hydrogen atom. Good quantum numbers correspond to observables commuting with Hamiltonian. Quantum numbers take discrete values, unlike classical systems
Hydrogen atom contains single proton and electron bound by Coulomb force. Atomic hydrogen constitutes about 75% of universe's baryonic mass. Most common isotopes are protium (99.985%), deuterium (0.0156%), and tritium (12.32 years)
Electrons fill orbitals in order of lowest energy level first. No two electrons can have same four quantum numbers. Electrons fill with same spin before opposite spin. Orbitals fill by sum of n and l values
Electrons occupy orbitals using quantum numbers n and l. No more than two electrons can occupy the same orbital. Orbitals are divided into shells (n=1-4) and subshells (s, p, d, f). Most stable orbitals have smallest n and l values
Electrons travel in circular orbits around nucleus with quantized sizes and energies. Bohr's model explains electrons' existence only in specific allowed orbits. Electrons can jump between orbits, emitting or absorbing energy. Energy changes produce photons when electrons move between levels