1 / 8

Inside the atom

Inside the atom. A beginners guide to atomic physics. Brief History. JJ Thomson Discovered the electron Where is it? Plum pudding Model. Rutherford Gold foil experiment Positive nuclear core. Problems with classical model.

gary-stuart
Télécharger la présentation

Inside the atom

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Inside the atom A beginners guide to atomic physics

  2. Brief History JJ Thomson • Discovered the electron • Where is it? • Plum pudding Model • Rutherford • Gold foil experiment • Positive nuclear core

  3. Problems with classical model • Coulomb force could make electrons orbit nucleus like planets, BUT… • Accelerated charge is supposed to emit EM waves…why is atom stable? • Also, why do atoms emit and absorb only discrete frequencies of radiation?

  4. BOHR ATOM • Circular electron orbits • Only “stationary” orbits allowed • The energy of each orbit is given by: En= (-13.6 eV) 1/n2(where n is an integer) • Photons of the correct energy are absorbed, “exciting” the atom into a higher energy orbit • Photons are emitted when the electron makes a transition to a lower energy orbit • The energy of the photons corresponds to energy difference of the two orbits DE=hf

  5. Bohr atom (continued) Bohr atom...java applet • What wavelength of radiation would excite the hydrogen atom from the ground state (E1) to the third energy level? E1 = -13.6 eV/1 = -13.6 eV E2 = -13.6/9 = -1.5 Ev hc/l = 12.1 eV l = 1243 eV-nm / 12.1 eV = 100 nm

  6. What possible wavelengths of light could be emitted when a hydrogen atom “de-excites” from the 4th energy level? -0.82 eV -1.51 eV -3.4 eV -13.6 eV

  7. Stationary orbits • Conservation of energy: KE + PE = Etot ½ mv2 – ke2/r = Etotal • Circular motion: F=ma  ke2/r2 = mv2/r  ke2/r = mv2 • Combined: Etotal= mv2 – ½ mv2 = -½ mv2 OR Etotal = ½ ke2/r – ke2/r = -½ ke2/r

  8. Stationary orbits (continued) • Which orbits are allowed? • One way of getting the answer is to look at deBroglie wavelength of electrons. • l=h/mv • To “fit” in a particular orbit, 2pr=nl

More Related