Max Planck ( )

German physicist Founder of the quantum mechanics theory Nobel Prize in 1918 for physics Assumed energy can be released or absorbed by atoms only in discrete “chunks”

Quantum- smallest quantity of energy that can be emitted or absorbed as electromagnetic radiation E=hv (energy of single quantum= constant x frequency) h= Planck’s constant = 6.3 x J-s

Albert Einstein ( )

German theoretical physicist Contributed to quantum theory and statistical mechanism Statistical mechanics- application of statistics to the field of mechanics (deals with motion of particles when subjected to force) 1921 Nobel Prize in physics for his work on photoelectric effect most famous for his Theory of Relativity E= mc 2

Photoelectric effect Einstein’s explanation: Light consists of particles, called photons, and Einstein deduced that each photon must have energy proportional to the frequency of light Energy of photon= E = hv

Niels Bohr ( )

Danish physicist Contributions to atomic structure and quantum mechanics 1922 Nobel Prize in Physics Most noted for his model of the hydrogen atom, also known as the Bohr Model theory that electrons travel in discrete orbits around the nucleus, and the chemical properties of the element are determined by the number of electrons in each of the outer orbits

Bohr Model Introduced two major ideas 1.Electrons exist only in certain discrete energy levels, which are described by quantum numbers 2.Energy is involved in moving an electron from one level to the next level His model dealt only with the hydrogen atom, so it acts as a stepping stone to a more comprehensive model

Louis de Broglie ( ) Worked on Wave Mechanics between 1930 and 1950 Awarded Nobel Prize in Physics "for his discovery of the wave nature of electrons” in 1929

The de Broglie Equations For a particle at rest, he equated the rest mass energy mc² to the energy of the quantum of the electromagnetic field h. That is, mc² = h where h is Planck's constant and c is the speed of light. This equation relates the wavelength to the particle momentum as where λ is the wavelength, h is Planck’s constant (6.63E-34), and p is the particle's momentum (the greater the energy, the larger the frequency and the smaller the wavelength. Short wavelengths are more energetic than long wavelengths) These de Broglie equations relate the frequency of a particle to the kinetic energy: where Ek is the kinetic energy, is the reduced Planck’s constant, k is the wavenumber, and ω is the angular frequency.

relationship between the motion of a particle and the associated de Broglie phase wave Particle = red circle de Broglie phase wave = green wave de Broglie hypothesis: all matter has a wave-like nature (wave-particle duality); that the wavelength is inversely proportional to the momentum of a particle and the frequency is directly proportional to the particle's kinetic energy. Copyright © 1997 by Davis Associates, Inc. All Rights Reserved

Experimental Confirmation Clinton Davisson and Lester Germer fired slow-moving electrons at a crystalline nickel target The angular dependence of the reflected electron intensity was measured and was determined to have the same diffraction pattern as those predicted by Bragg for X- Rays The presence of any diffraction effects by matter demonstrated the wave-like nature of matter Experiment showed the wave-nature of matter, and completed the theory of wave- particle duality Idea was important because it means that not only can any particle exhibit wave characteristics, but that one can use wave equations to describe phenomena in matter if one uses the de Broglie wavelength The top half is an example of X-ray diffraction, the bottom of electron diffraction

Werner Heisenberg ( ) Born in Würzburg Germany Published Theory of Quantum Mechanics in 1925 Given 1932 Nobel Prize in Physics for his findings and their applications Head of Germany’s nuclear energy program Worked on plasma physics and thermonuclear processes after 1957

The Uncertainty Relations principle of uncertainty- the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory. The very concepts of exact position and exact velocity together have no meaning.  x  p x > h / 2  x is the uncertainty of the position.  p x is the uncertainty of the momentum h is Planck's constant It is impossible to measure an atomic system without affecting it

Experimentation Gamma-ray microscope described in Heisenberg's paper on the uncertainty principle. The blue circle is the particle, the green wave is the incoming gamma-ray and the red wave is the gamma-ray scattered up into the aperture angle θ of the microscope (depicted as solid black lines). The uncertainty in the particle position is Δx, as shown.

Wolfgang Pauli ( ) Born in Vienna Developed the foundations of Quantum Theory; made great scientific advances in the field Received Nobel Prize in Physics in 1945

Electron Spin Intrinsic property of electrons Electron behaves as if it were a sphere spinning on an axis Consolidated field theory by giving proof of the relationship between spin and"statistics" of elementary particles Spin magnetic quantum # (m s ): +1/2 OR -1/2

Experiment for Electronic Spin Performed by Stern and Gerlach Beam of neutral atoms shot through a magnet; the electrons with a +1/2 charge deflected one way, electrons with a –1/2 charge deflected another way

Pauli’s Exclusion Principle No two electrons in an atom can have the same values for n (shell#), l (azimuthal quantum#, defines shape), m l (magnetic quantum#, orientation of the orbital in space) and m s Explains why matter occupies space exclusively for itself and does not allow other material objects to pass through it, at the same time allowing lights and radiations to pass Therefore, an orbital can hold a maximum of 2 electrons (must have opposite spins) No Electrons Here +

Erwin Schrödinger Born in Erdberg, Vienna. At age 11 – attended the Akademisches Gymnasium. Age – studied in Vienna under Franz Serafin Exner and Friedrich Hasenöhrl. Conducted experimental work with Friedrich Kohlrausch – attended the University of Zurich – published "Quantisierung als Eigenwertproblem“ on wave mechanics, otherwise known as the Schrödinger equation – Schrödinger’s cat experiment.

Schrödinger’s Cat A cat (imaginary!) is placed in a box A radioactive atomic nucleus and a canister of poison gas is attached to the box There is a 50% chance of the nucleus will decay in one hour. If the nucleus decays, it will emit a particle that triggers an apparatus that opens the canister and kills the cat. If the nucleus does not decay, the cat remains alive. According to quantum mechanics, the unobserved nucleus exists of a “decayed nucleus” and “undecayed nucleus.”

The Problem: If “the unobserved nucleus exists of a decayed nucleus and undecayed nucleus,” Schrödinger explained that “the wavefunction for the entire system would have the living and dead cat mixed or smeared out in equal parts.” –So supposedly, the wavefunction collapses and the cat is either dead or alive instead of a mixture of both.

Otto Stern Born in Sohrau and studied at Breslau. Professor of physics at Carnegie Institute of Technology and University of California, Berkeley. Contributed to the molecular ray method, discovery of spin quantization (Stern-Gerlach experiment), measurement of atomic magnetic moments, wave nature of atoms and molecules, and the discovery of the proton’s magnetic moment.

Walther Gerlach Born in Biebrich am Rhein, Germany Educated at the University of Tübingen. Became a professor of physics at Tübingen in 1925 and at Munich from Worked with Otto Stern. Contributed in the fields of radiation, spectroscopy, quantum theory, and the Stern- Gerlach experiment.

Stern-Gerlach Experiment If the particle travels through a magnetic field, then the force on one end of the electron will be slightly greater than the other side. –Causes deflection in the magnetic field Distribution of spin angular momentum vectors supposed to be random, but the experiment showed that the particles are either deflected up or down by a specific amount.. –This means that spin angular momentum is limited and can only take on discrete values.

Timeline of Quantum Theory Max Planck: meaning of quantum, Planck’s constant Albert Einstein: the Photoelectric Effect Niels Bohr: line spectra & Bohr’s Atom Model Stern-Gerlach Experiment: deflection of particles Louis de Broglie: wave model of the electron Wolfgang Pauli: Pauli Exclusion Principle Erwin Schr ö dinger: Theory of Wave Mechanics Werner Heisenberg: Matrix Mechanics Heisenberg, Born, & Jordan: Theory of Electrodynamics Werner Heisenberg: Uncertainty Principle