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Quantum Mechanical Model. CHM 108 Suroviec Fall 2014. I. Quantum Mechanics. Small is a relative term, but we use it to show size. There is a limit to how we can use it in science. II. Nature of Light. A. Wave Nature of light
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Quantum Mechanical Model CHM 108 Suroviec Fall 2014
I. Quantum Mechanics • Small is a relative term, but we use it to show size. • There is a limit to how we can use it in science.
II. Nature of Light A. Wave Nature of light Light is electromagnetic radiation. A type of energy embodies in oscillating electric and magnetic fields
A. Wave Nature of Light • An EM wave can be characterized by its amplitude and wavelength.
A. Nature of Light • All waves are also characterized by frequency (n)
B. The EM Spectrum • The EM Spectrum is made of several different wavelengths
C. Interference and Diffraction • Waves (including EM waves) interact with each other in a characteristic way called interference
D. Particle Nature of Light • In the early 1900s light was believed to be wave only, but then the photoelectric effect was discovered.
Example • A DVD player uses a laser that emits light at 685nm. What is the energy of 1 mole of photons of this light?
III. Atomic Spectroscopy and the Bohr Model • The dual nature of light led scientists to think about how light acts as both a particle and as a wave. • Atomic Spectroscopy was developed to explore the phenomenon.
III. Atomic Spectroscopy and the Bohr Model • The idea that each element has discreet lines required scientists, like Neils Bohr, to develop a new model for the atom.
IV. Wave Nature • It has been shown that the wave nature of an electron is an inherent property of an individual electron. • deBroglie Wavelength • An electron traveling through space has a wave nature.
Example • Calculate the wavelength in nm of an electron with speed 4.57 x 106 m/s
B. Uncertainty Principle • Experiments have shown that we can never see the interference pattern and simultaneously determine which hole the electron goes through to make it.
C. Indeterminacy • Macroscopic objects have their velocity and position known : determined. • Electrons do not (Uncertainty Principle): indeterminacy
V. Quantum Mechanics and the Atom • Many properties of an element is dependent on the energy of electrons which is related to the velocity which we have shown to be indeterminate. • Schrodinger Equation • The wave function ψ is away to describe energy of electrons and the probability of finding an electron in a volume of space.
1. Principle Quantum Number (n) • The integer that determines overall size and energy of an orbital.
2. Angular Momentum Quantum Number (l) • This number determines the shape of the orbital.
3. Magnetic Quantum Number (ml) • This number tells us the orientation of the orbital
ml = -1 ml = 0 ml = 1 ml = -2 ml = -1 ml = 0 ml = 1 ml = 2
4. Magnetic Spin Number (ms) • The spin of the electron in the orbital
Examples • How many 2p orbitals are there in an atom? • How many electrons can be placed in the 3d sublevel?