Chapter 12 Study Guide

# Chapter 12 Study Guide - Chapter 12 Study Guide...

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Chapter 12 Study Guide Electromagnetic radiation : radiant energy that exhibits wavelike behavior and travels through space at the speed of light in a vacuum Wavelength : the distance between two consecutive peaks or troughs in a wave Frequency : the number of waves(cycles) per second that pass a given point in space Wavelength (lambda) and frequency (nu) are inversely related (lambda)( v ) = c Ultraviolet catastrophe : a radiation profile that has no maximum and goes to infinite intensity at very short wavelengths Planck’s constant : the constant relating the change in energy for a system to the frequency of the electromagnetic radiation absorbed or emitted; equal to 6.626 x 10 -34 J S Energy can be gained or lost only in integer multiples of hv Planck’s constant = 6.626 x 10 -34 J s E = nhv Quantization : the concept that energy can occur only in discrete units called quanta Photon : a quantum of electromagnetic radiation G. N. Lewis coined the term photon in 1926 E photon = hv = hc / (lambda) Photoelectric effect : the phenomenon in which electrons are emitted from the surface of a metal when light strikes it 1) Studies in which the frequency of the light is varied show that no electrons are emitted by a given metal below a specific threshold frequency vo 2) For light with frequency lower than the threshold frequency, no electrons are emitted regardless of the intensity of the light 3) For light with frequency greater than the threshold frequency, the number of electrons emitted increases with the intensity of the light 4) For light with frequency greater than the threshold frequency, the kinetic energy of the emitted electrons increases linearly with the frequency of the light E = mc 2 : Einstein’s equation proposing that energy has mass; E is energy, m is mass, and c is the speed of light Dual nature of light : the statement that light exhibits both wave and particulate properties Lambda = h / mv

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Diffraction : the scattering of light from a regular array of points or lines, producing constructive and destructive interference Diffraction pattern : bright areas and dark spots on a photographic plate caused by scattered radiation Continuous spectrum: a spectrum that exhibits all the wavelengths of visible light Line spectrum: a spectrum showing only certain discrete wavelengths The energy of the electron in the atom is quantized Quantum model : electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits E = -2.178 x 10 -18 J ( Z 2 / n 2 ) This equation applies to all one-electron species including Li 2+ , He +
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