Quantum Model of the Atom l Bohr l de Broglie l Heisenberg l Schrödinger

Neils Bohr (1885 –1962) Bohr Model of the Hydrogen Atom

Bohr model of the atom In the Bohr model, electrons can only exist at specific energy levels (orbit). Energy

Photo Absorption and Emission

Hydrogen Line Spectrum Balmer Series

Line Spectra Line spectrum of Hydrogen is produced when an electron drops from a higher-energy orbit to a lower energy orbit. Specifically, E photon = E 2 - E 1 = h Specifically, E photon = E 2 - E 1 = h

Bohr Checked it with Math. l Used mass and charge of the electron together with Planck’s constant and calculated where the spectral lines should be and they were! l Problem -- only worked for Hydrogen!

Bohr model of the atom l The Bohr model is a ‘planetary’ type model. l Each principal quantum represents a new ‘orbit’ or layer. l The nucleus is at the center of the model.

Hydrogen Spectrum (cont.) Each line of the Hydrogen spectrum is produced by and corresponds to the emission of photons with specific energies (E = h )

Bohr Model Holt Online Learning Holt Online Learning

What the Heck is Light?

Hold It! l Nay, Nay says “Classical” theory. l Hydrogen should be excited by whatever amount of energy. l Should be continuous spectrum l What’s with the lines????

l Why wouldn’t there be an infinite number of energy levels for electrons? l Photoelectric effect and Hydrogen spectrum.

Neils Bohr (1885 –1962) Bohr Model of the Hydrogen Atom

Louis de Broglie ( ) Electrons should be considered waves confined to the space around an atomic nucleus

The Quantum Atom (cont.) l Since electrons are waves, they can amplify and cancel out when in and out of sync. l Therefore only certain energies of electrons are possible.

Werner Heisenberg Heisenberg Uncertainty Principle – It is impossible to determine the position and velocity of an electron simultaneously.

Separated at Birth….

Heisenberg uncertainty principle l In order to observe an electron, one would need to hit it with photons having a very short wavelength. l Short wavelength photons would have a high frequency and a great deal of energy.

Heisenberg uncertainty principle l If one were to hit an electron, it would cause the motion and the speed of the electron to change. l Lower energy photons would have a smaller effect but would not give precise information.

Heisenberg Uncertainty Principle Holt Online Learning Holt Online Learning

Erwin Schrödinger ( ) Schrödinger developed the calculus to describe the wave behavior and energies of electrons in atoms.

Schrödinger’s Equation Yeah, but it works!

Bohr vs. Schrödinger Orbits vs. Orbitals Bohr -- definite distinct orbits populated by electron particles.

Bohr vs. Schrödinger Orbits vs. Orbitals Schrödinger -- electron are waves (de Broglie) with a certain probability (mathematical model) of being found in three dimensional regions around the nucleus - orbitals

Comparing Models of the Atom – A review Holt Online Learning Holt Online Learning