Louis de Broglie, (France, ) Wave Properties of Matter (1923) -Since light waves have a particle behavior (as shown by Einstein in the Photoelectric Effect), then particles could have a wave behavior. Photoelectric Effect -He suggested electrons could be considered waves confined to a space around an atomic nucleus

Evidence for De Broglie Hypothesis -Davisson and Germer showed experimentally that electrons can, like light waves, diffract. -Other researchers demonstrated interference with electrons, another property of waves. -Much of this research revealed results that matched De Broglie’s calculated electron wavelengths. -De Broglie won the Nobel Prize in 1929 for this concept.

Light versus Electron Diffraction

Electrons: Waves and Particles? Big problem …. If electrons are both particles and waves, then where are they in the atom?

Werner Heisenberg: Uncertainty Principle We can not know both the position and momentum of a particle at a given time. (1927)

Erwin Schrodinger, 1925 Quantum (wave) Mechanical Model of the Atom -Developed equation (wave equation) that treated electrons in atoms as waves. -Only waves of specific energies provided solutions to his equation. -Along with Heisenberg principle, this wave equation laid the foundation for modern quantum theory

What Schrodinger’s Equation Means to Chemists -Electrons do not travel around the nucleus in neat orbits. -We only have a probability of finding an electron at a given place around the nucleus. -Electrons exist in orbitals that have three dimensional shapes. These orbital shapes are described by the solutions to Schrodinger’s wave equation for different energies. -Property of orbitals can be described by 4 quantum numbers.

Four Quantum Numbers -Principal Quantum Number (n) -Orbital Quantum Number (l) -Magnetic Quantum Number (m) -Spin Quantum Number