Key Terms
Wave-particle duality
Light behaves as a wave in interference experiments and as a particle (photon) in the photoelectric effect. Both are tru
Continuous spectrum
All wavelengths present (white light, sunlight, heated solids).
Line spectrum
Only specific discrete wavelengths emitted; unique to each element. Used to identify elements remotely, including in sta
Core assumptions
1. Electrons orbit the nucleus in fixed circular orbits without radiating energy (stationary state hypothesis) 2.
Energy of a Bohr orbit
E_n = -k / n^2
Energy change between orbits
Delta E = k x (1/n_i^2 - 1/n_f^2)
Ground state
N = 1 (lowest energy, most stable) Excited state: any n greater than 1
Electron drops to lower energy
Photon emitted. Electron jumps to higher energy: photon absorbed.
Orbit radius
R = a_0 x n^2
Standard filling order
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p...
Example
Fe (Z=26): [Ar] 4s2 3d6 Fe2+: remove two 4s electrons first = [Ar] 3d6 (NOT [Ar] 4s0 3d6 with holes elsewhere)
Format
(n)(subshell letter)(superscript = number of electrons) Example: 2p4 means 4 electrons in the p subshell of shell n = 2.
Full example
Phosphorus (Z=15) 1s2 2s2 2p6 3s2 3p3
Abbreviated using noble gas core
[Ne] 3s2 3p3
Main group elements
Last electron added enters s or p orbital