Chapter 8 Outline - Chemistry 101 Vandan Desai Chapter 8:...

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Chemistry 101 Vandan Desai P a g e | 1 Chapter 8: The Quantum Mechanical Atom (Lecture Outline) --------------------------------------------------------------------------------------------------------------------------- I. Electromagnetic radiation can be described as a wave or a stream of photons A. Energy can be transferred between things as light or radiation B. Radiation carries energy through space as waves —an oscillation that moves outward from a disturbance i. Ex: ripples moving away from a pebble dropped into a pond ii. In the case of radiation, the disturbance can be vibrating electrical charge iii. Pulse in one field ( electric ) gives rise to a pulse in the other ( magnetic ) C. Resulting train of pulses in the electric and magnetic fields is called an electromagnetic wave i. The higher the vibrating charge bounces, the greater the height or amplitude Affects the intensity or brightness of the radiation ii. The number of cycles per second is called the frequency ( v ) Units of frequency are the hertz (Hz) ) second /( 1 s / 1 s 1 Hz 1 -1 = = = D. The minimum and maximum amplitude of electromagnetic radiation are evenly spaced E. The peak-to-peak distance is called the wavelength ( λ ) F. The product of frequency and wavelength give the speed of light ( c ) i. m/s 10 3.00 8 × = = × c υ λ G. Electromagnetic radiation comes in a broad range of frequencies called the electromagnetic spectrum i. Divided into regions according to the wavelengths of radiation ii. Light (or visible region ) is a small slice of electromagnetic that we see ”; wavelengths between about 400 and 700 nm iii. Gamma rays , X-rays , ultraviolet radiation = shorter λ , larger v iv. Microwaves , infrared radiation , and radio waves = longer λ , smaller v H. Plot of wavelengths absorbed vs. the absorption is called infrared absorption spectrum i. Since it is unique for every substance, it can be used to identify a substance I. The oscillating magnetic and electric fields of an electromagnetic wave interact with particles that it passes J. A charged particle can pick up energy at the expense of the radiation source K. In 1900, the German scientist, Max Plank , proposed that the electromagnetic radiation could be viewed as a stream of tiny energy packets or quanta we now call photons i. Photons travel at the speed of light ii. Plank proposed, and Einstein confirmed, that the speed of a photon is proportional to its frequency
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Chemistry 101 Vandan Desai P a g e | 2 iii. Energy of a photon = E = hv ( h = Planck’s constant = 6.626 x 10 -34 Js ) L. If a particular event requiring energy is initiated, frequency ( energy of photons ) is important , not brightness or intensity ( number of photons ) M. This means that both electron and electromagnetic radiation can be represented as either waves or particles II. Atomic line spectra are experimental evidence that electrons in atoms have quantized energies A. The visible spectrum is a continuous spectrum b/c it contains a continuous distribution
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This note was uploaded on 10/19/2010 for the course CHEM 121 taught by Professor Harris during the Fall '09 term at Community College of Baltimore County.

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Chapter 8 Outline - Chemistry 101 Vandan Desai Chapter 8:...

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