Models of the hydrogen atom

Issues with Rutherford model

• Why don’t electrons just spiral into nucleus?

• Why don’t positive charges in nucleus repel each other?

Inquiring minds want to know…

Neils BohrJames Chadwick

The big question…• What model of electrons in a

hydrogen atom explains this?

Bands of colorElectric current thru H2 gas

Predicted spectrum models vs. experimental

No bands

One band in UV

Almost all bands match, ratios better

Almost all bands match, ratios best

Most bands match, ratios ?

Explaining models match to H-spectrum

• Billiard ball – no bands, no interaction of light with H-atom

• Plum pudding – one band, interaction of light with H-atom but only one transition

• Bohr – most bands match, ratios of band heights not matching

• DeBroglie – almost all bands match, ratios match better

• Schrodinger - almost all bands match, ratios match best

Quantum Mechanics video

Explaining Bohr model of H atom

Steps to create spectrum in Bohr model

1. Incoming photon excites electron to a higher shell– Photon must be high enough energy

2. Electron “chooses” to drop (relax, decay) to a lower shell– “When” and “which shell” completely unknown

3. When relaxes, excess electron energy is released as a photon of light

– Energy of photon corresponds to difference in energy levels

Bohr model of atom

http://www.bigs.de/en/shop/anim/termsch01.swf

Explaining power of quantum model

BaCl2 CuCl2 KCl LiCl NaCl

Explaining powerFireworks!!!

Explaining powerLuminescent paper

Properties of a good explaining theory…

• A good explaining theory – Is simple– Explains all the data

• Doesn’t contradict itself • Connects previously

unconnected data– Is fruitful

• Leads to new experiments– Links to other theories