1. Models of the Atom Chapter 4 Chm 1.1.2 and 1.1.3

2. Model: Neils Bohr e- circles nucleus in allowed paths, “orbits” Each orbit has a fixed energy e- cannot exist between energy levels e- in orbit farther from nucleus have higher energy e- in orbit closest to the nucleus have lowest energy

3. The Bohr Model Purpose To explain the hydrogen line emission spectrum To explain why atoms of hydrogen give off light

4. The Hydrogen Line Emssion Spectrum Pink light emitted from hydrogen when exposed to electric current Specific wavelengths and frequency of light Electromagnetic radiation - LIGHT

5. Light Electromagnetic radiation Gamma, Xrays, UV, Visible, IR, Microwaves and Radio waves Visible Light: Violet, Blue, Green, Yellow, Orange and Red

7. Wavelength (λ) – distance between 2 wave peaks (m or nm) Frequency (ν) – the number of wave peaks per second (Hertz) Photon – a particle of electromagnetic radiation having no mass and carrying a quantum of energy Quantum – the minumum amount of energy that can be lost or gained by an atom

8. How atoms give off light…

9. Using the Bohr Model to predict light Example: –What color light is emitted by the hydrogen atom when an electron transitions from n = 3 to n = 2? –What wavelength is released when an electron falls from n = 4 to ground state –What type of electromagnetic radiation is released when an electron falls from n = 4 to n = 3?

10. Particle Wave-Duality Electrons are made of particles (photons) They exhibit wave behavior

11. The Quantum Model The electron cloud model The Heisenberg Uncertaininty principle – it is impossible to know exact location of electron Only a probably location is known Electron do not orbit 2D Electron are found in a probable 3D region of space around the nucleus Probability Model

12. Bohr vs Electron Cloud