CHAPTER 7

# CHAPTER 7 - CHAPTER 7 Atomic Structure and Periodicity 7.1...

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Unformatted text preview: CHAPTER 7- Atomic Structure and Periodicity 7.1 Electromagnetic radiation- energy that exhibits wavelike behavior and travels at the speed of light in a vacuum. Wavelength- ( λ ) distance between crests or troughs Frequency- (v_ number of wave cycles per second that pass a given point in space -there is an inverse relationship between wavelength and frequency • λ v=c [ λ is in meters, v is cycles per second, and c is the speed of light (2.9979 * 10 8 meters per second)] SAMPLE 7.1 The brilliant red colors seen in fireworks are due to the emission of light with wavelengths around 650 nm when strontium salts such as Sr(NO 3 ) 2 and SrCO 3 are heated. (This can be easily demonstrated in the lab by dissolving one of these salts in methaonol that contains a little water and igniting the mixture in an evaporating dish.) Calculate the frequency of red light of wavelength 6.50 * 10 2 nm Answer: 6.5 * 10 2 nm x (1m)/10 9 nm) 6.50 * 10-7 m And v=c/ λ , so (2.9979 * 10 8 m/s) /(6.50 * 10-7 m) = 4.61 * 10 14 Hz. 7.2 The Nature of Matter-energy can be gained or lost in integer multiples of hv. E= nhv [n = an integer, h= Plank&s constant(6.626 * 10 ¡34 J*s), and v =frequency] -Energy is quantized and can only occur in discrete units of size hv (¢packets£ of energy called quanta) SAMPLE 7.2 The blue color in fireworks is often achieved by heating copper(I) chloride(CuCl) to about 1200 û C. Then the compound emits blue light having a wavelength of 450 nm. What is the increment of energy (the quantum) that is emitted at 4.50 * 10 2 nm by CuCl? Answer: -v=c/ λ , so (2.9979 * 10 8 m/s)/(4.50 * 10-7 m) = 6.66 * 10 14 s-1 . And E=hv=(6.626 * 10-34 J*s)(6.66 * 10 14 s-1 ) =4.41* 10-19 J. -EMR can be viewed as a stream of particles called photons E photon = hv= (hc) / λ-Einstein&s special theory of relativity, E= mc 2 • m= E/c 2 and E photon = hc/ λ , so m = (hc/ λ )/c 2 = h/(c λ ) -EMR seems to have characteristics that of waves and particles and this phenomenon is sometimes referred to as the dual nature of light -matter can exhibit wavelike properties de Broglie equation m = h/c λ = h/v λ , so λ = h/mv SAMPLE 7.3 -diffraction- results when light is scattered from a regular array of points or lines - constructive interference- (in phase) peaks of one wave match the peaks of...
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## This note was uploaded on 09/27/2010 for the course CHEM 210 taught by Professor Mcomber during the Spring '10 term at Skyline College.

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CHAPTER 7 - CHAPTER 7 Atomic Structure and Periodicity 7.1...

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