The Bohr Atom

Thompson: plum pudding

Rutherford: nucleus in a sea of electrons.

Bohr: planetary model.

Wave velocity = (wavelength)(frequency).

Review of wave mechanics.

The electromagnetic spectra: The type of wave is determined by its wavelength and frequency.

Speed of light = 2.998 x 108 m/s

A light wave has a frequency of 1.74 x 1017 hertz. What is its wavelength? What type of light is it?

Planck’s Hypothesis

Light is given off in bundles of energy called quanta.

E = h(

Energy = planck’s constant * wave frequency

h = 6.626 x 10-34 J/hz

Energy Problems

A photon of light is found to have 3.63 x 10-22 Joules of energy. What is the wavelength of this light wave?

A photon of light is found to have a wavelength of 5.00 x 102 nm. What is the energy of a photon of this light wave?

Planck’s Hypothesis

Atomic Spectra: produced when an electron moves from a higher to lower energy level, giving off light in the process.

(E = Ehi - Elo = h( = hc/(

Ex. For the yellow line in the sodium spectra (( = 589.0 nm), find its frequency, quantum energy, and the energy released by one mol of sodium electrons.What is the energy difference between two energy levels of Na?

Planck’s Hypothesis

( ( 5.090 x 1014s-1

(E = 3.373 x 10-19 J

For one mol of electrons: (E = 203.1 kJ

Hence a two energy level difference = 203.1 kJ/mol

Bohr Model

Bohr postulated that an electron moves about the nucleus in a circular orbit of a fixed radius.

The emission spectra of hydrogen: hydrogen absorbs energy when excited then gives it off when it returns to its ground state.

The ground state of an electron represents its lowest orbit. The excited state represents any other possible orbit.

Hydrogen only emits this absorbed energy at certain visible...