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II. Bohr Model of the Atom

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Electrons in Atoms

II. Bohr Model of the Atom

- NielsHenrik David Bohr 1885 - 1962
- Born 1885, Copenhagen, Denmark.
- Father was an eminent physiologist.
- 1911 - Studied and worked at Cambridge under Sir JJ Thomson
- 1912 – worked in Ernest Rutherford’s lab in Manchester, England.
- 1922 – Nobel Prize in Physics for work on the structure of atoms.

- e- exist only in orbits with specific amounts of energy called energy levels
- Therefore…
- e- can only gain or lose certain amounts of energy
- only certain photons are produced

excited state

ENERGY IN

PHOTON OUT

ground state

Energy of photon depends on the difference in energy levels

Bohr’s calculated energies matched the IR, visible, and UV lines for the H atom

6

5

4

3

2

1

- Each element has a unique bright-line emission spectrum.
- “Atomic Fingerprint”

Helium

- Bohr’s calculations only worked for hydrogen!

Electrons in Atoms

III. Quantum Model of the Atom

- Louis de Broglie (1924)
- Applied wave-particle theory to e-
- e- exhibit wave properties

QUANTIZED WAVELENGTHS

VISIBLE LIGHT

ELECTRONS

EVIDENCE: DIFFRACTION PATTERNS

- Heisenberg Uncertainty Principle
- Impossible to know both the velocity and position of an electron at the same time

- SchrödingerWave Equation (1926)
- finite # of solutions quantized energy levels
- defines probability of finding an e-

Radial Distribution Curve

Orbital

- Orbital (“electron cloud”)
- Region in space where there is 90% probability of finding an e-

- Summary of Quantum Theory
- Describes mathematically the wavelike properties of e-1 and other small particles.
- Applies to ALL atoms (unlike the Bohr model)
- Supports the idea that e-1 exist in regions called orbitals where there is a probability of finding them.
- Ask me about the 4th bullet point

- Organization of electrons in atoms
- Energy levels
- Sublevels
- Orbitals