Chapter 23: Atomic Physics 🏁

Early model of the Atom

Rutherford

  • Positive charge is concentrated in the center of the atom, nucleus

Atoms emit cetain discrete characteristics frequencies of electromagnetic radiation

  • Rutherford model is unable to explain this phenomena
  • Atom will not stable

J.J. Thompson's :

  • Electrons embedded through out volume
  • A change from Newton's model of the atom as a tiny,hard,indestructible sphere

Bohr's theory of the hydrogen atom
Assumptions: The electron moves in circular orbits around the proton under the influence of the coulomb force of attraction.

Angular momentum: angular

Centripetal force: cf

notes

notes 2

Radiation:

  • emitted by the atom when the electron "jumps"
  • from allowed orbit to another allowed orbit

Electron Energy:
addition

Energy of electrons

Potential Energy: potential

Kinetic Energy: kinetic

Total Energy: total

model

  • "jump" cannot be treated classically
  • frequency of radiation emitted in the "jump" is related to the charge in the energy of the electron

Ei-Ef=hf

Hydrogen Energy Levels

E = -E0/n2, where E0 = 13.6 eV (1 eV = 1.602×10-19 Joules) and n = 1,2,3…

The hydrogen spectrum

  • Each line has a different wavelength and color

Formula

  • Erad=Ei-Ef
  • Erad=hf=hc/λ

Pauli's exclusion principle

  • No two electrons can have the same set of quantum number

ee

Atomic spectra

  • At ordinary low temperatures, most of the atoms in a sample are in the ground state.
  • Only photons with energies equal to differences between energy levels can be absorbed/emitted.

X-rays

  • Electrons are emitted from a heated filament and accelerated through a large voltage
  • Higher orbital electrons then jump to occupy the vacant space
  • X-rays are emitted

x trays

xtrays 2

Laser

  • High voltage applied causes electrons to sweep through the tube, producing excited states
  • Electron falls to E2 from E*3 in Ne, a 632.8nm photon is emitted

laser

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