The Quantum Mechanical Model of the Atom • Outline • Light • Atomic Spectra • Bohr’s Model of the Atom • Wave-Particle Duality • de Broglie Wavelength • Uncertainty Principle • Quantum Mechanical Atom • Schrodinger Equation • Quantum Numbers, n, l, ml, ms • Orbitals Chapter 7
Can you see interference patterns generated by the diffraction of light between your fingers?
Chapter 7: Examples – EMR Radioastronomers use 1,420 MHz waves to look at interstellar clouds of hydrogen atoms. • What is the wavelength of this radiation? • What is the wavenumber?
low frequency and energy high frequency and energy Types of Electromagnetic Radiation • Electromagnetic waves are classified by their wavelength • Radiowaves = l > 0.01 m • Microwaves = 10−4 < l < 10−2 m • Infrared (IR) • far = 10−5 < l < 10−4 m • middle = 2 x 10−6 < l < 10−5 m • near = 8 x 10−7< l < 2 x 10−6m • Visible = 4 x 10−7 < l < 8 x 10−7 m • ROYGBIV • Ultraviolet (UV) • near = 2 x 10−7 < l < 4 x 10−7 m • far = 1 x 10−8 < l < 2 x 10−7 m • X-rays = 10−10 < l < 10−8m • Gamma rays = l < 10−10 Tro: Chemistry: A Molecular Approach, 2/e
Chapter 7: Examples – EMR A stop light has a red (700 nm), yellow (580 nm) and green (530 nm) lights. Which has the highest frequency?
2-Slit Interference Tro: Chemistry: A Molecular Approach, 2/e
Quantization of energy • Energies in atoms are quantized, not continuous. • Quantized means only certain energies allowed.
Chapter 7: Examples – EMR Calculate the energy of one quantum of red light (700 nm).
Chapter 7: Examples – EMR A certain lamp produces 5.0 J/s of energy in the blue region of the spectrum. How many photons of blue (470 nm) light would it generate if it were left on for 8.5 s?
Chapter 7: Examples – EMR If a light with a wavelength of 200 nm shines on sodium atoms with an ionization energy of 496 kJ/mol, what will be the speed of the electrons emitted?
Experiment 1 • Add an elemental gas to a cathode ray tube and get ----- colors • Hydrogen (H2) purple blue • Neon (Ne) red orange • Helium (He) yellow pink • Argon (Ar) lavender • Xenon (Xe) blue
Experiment 2 • Shine white light through a prism -- rainbow • A prism separates light of different wavelength, each color represents a different wavelength. Sundog – caused by ice acting as a prism.
Experiment 3 • Shine the colored light from our gas discharge tubes through a prism get distinct bands of color (light).
Examples of Spectra Tro: Chemistry: A Molecular Approach, 2/e
Emission vs. Absorption Spectra Spectra of Mercury Tro: Chemistry: A Molecular Approach, 2/e
Chapter 7: Examples – EMR Calculate the wavelength of a photon emitted by a hydrogen atom when an electron makes a transition between the third and second principle quantum level.
John Dalton p124
Chapter 7: Examples – Energy Quantization A stream of laser photons has a frequency of 7.57 x 1014 Hz. • What is it’s energy? • What level can it get to?
Chapter 7: Examples – de Broglie • What is the wavelength in nm associated with a 0.080 kg ball moving at 70.0 km/hr? • How fast must the ball travel to have a wavelength of 0.0500 nm?
Trajectory vs. Probability Tro: Chemistry: A Molecular Approach, 2/e
Electron Spin Experiment Tro, Chemistry: A Molecular Approach
·equal to +1/2 or 1/2 ·necessary because each orbital contains 2 electrons and each electron needs its own space. Spin quantum number (ms)
Chapter 7: Examples – Quantum Numbers If n = 4, l = 2, ml = +2, what type of orbital is the electron located?
Chapter 7: Examples – Quantum Numbers Give the possible combination of quantum numbers for a 3s1 orbital.