The Development of a New Atomic Model - 4.1

 Problem with Rutherford model – no explanation of where e-s are  New info about light led to new model of the atom  Before 1900 scientists thought light traveled like a wave.  We know now that light behaves like a wave and like a particle

 Called the dual wave-particle nature of light!  Electromagnetic Radiation - form of E that exhibits wavelike behavior as it travels thru space  Electromagnetic Spectrum - all of the forms of electromagnetic radiation (visible light, x-rays, uv and infrared light, micro and radio waves)

 All types of emag rad. move at 3.00 x 10 8 m/s in a vacuum. (slightly slower thru matter)  This is the speed of light

 Wavelength - λ the distance between corresponding points on adjacent waves  Frequency - ν the number of waves that pass agiven point in a specific time, usually 1 second  Frequency is expressed in Hertz (Hz)

 c = λν  The speed of light = wavelength times frequency  The wavelength of red light is 7.6 x m, calculate the frequency.  F = speed = x 10 8 m/s wavelength 7.6 x m  Frequency = 3.9 x Hz

 The emission of e-s from a metal when light shines on the metal  Light had to be a certain freq. to emit e-s

 Planck proposed idea of quanta (E packets)  Quantum of energy - the minimum quantitiy of E that can be lost or gained by an atom

 E = h ν  Where E is the energy in joules of a quantum of radiation  υ is the frequency in s -1  h is Planck's constant of x J * s

 Ein. supported Planck by proposing the duality of light as particle and wave  Ein. proposed particles of light carry a quantum of E called photons (0 mass)

 The E of a photon depends on the υ of rad.  E absorbed in whole # of photons  Different metals need diff. υ to remove an e-

Electric current passed thru a gas at a low pressure

LES = the result from a narrow beam of the emitted light that is shined through a prism when it separated into colors of the visible spectrum The Continuous Spectrum

 Ground state - the lowest E level of an atom (very stable level)  Excited state - a state in which an atom has a higher potential E than it has in its ground state

 When an e- falls from the excited state, a photon is given off - the E of the photon is = to the E difference  H only emits certain freq. so e- exists in specific E levels