CHM135H1 Lecture Notes - Lecture 1: Microwave Oven, Work Function, Significant Figures

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Published on 8 Sep 2017
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Department
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Professor
Electrons*are*essential*for*ions,*bonding*etc
Electronic*structure*can*be*studied*by*looking*at*electromagnetic* radiation
Significant*figures*don’t*matter,*in*tests*it*has*to*be*in*the*ball*park
Electromagnetic*Radiation
Any*form*of*energy*traveling*as*waves*through*space
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Waves
Wavelength*-distance*between*2*peaks*or*troughs
1.
Frequency*-number*of*waves*per*second*that*pass*through*a*given*point*(cycles/s,*s-1,*Hz)
2.
The*higher*the*number*of*waves,*the*higher*the*frequency
Amplitude*-
3.
The*higher*the*wave*the*higher*the*amplitude
Electromagnetic*Spectrum
Microwave*oven*excites*the*water*molecules*in*food,*creating*kinetic*
energy*which*heats*up*the*food
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"light"*=*electromagnetic*radiation
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𝑣𝜆# = #𝒄
Photoelectric*effect
If**a*light*shines*on*a*metal,*only*some*electrons*come*off
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Current*flows*as*soon*as*light*of*minimum*frequency*hits*the*metal
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As*the*frequency*of*light*hitting*the*metal*increases,*the*higher*the*kinetic*energy*of*the*electrons*
coming*off*(it*increases*linearly)*
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Number*of*electrons*increase*with*intensity*of*light,*but*not*kinetic*energy
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Photons
Bundles*of*light*with*energy
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Ephoton#= #ℎ𝑣# = '(
)
If*the*frequency*of*light*hitting*metal*is*low,*no*electron*comes*off
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The*minimum*energy*needed*to*eject*electron*is*called*work*function
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If*photons*have*enough*energy,*the*electrons*from*metal*can*come*off*
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hv*=*ϕ+*Keelectron
The*lower*the*threshold*of*the*metal,*the*less*energy*needed*by*the*photons*to*eject*
electrons
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Electronic*Structure*of*Atoms
Wednesday,* September* 6,*2017
10:35*PM
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Document Summary

Electronic structure can be studied by looking at electromagnetic radiation. Significant figures don"t matter, in tests it has to be in the ball park. Any form of energy traveling as waves through space. Wavelength - distance between 2 peaks or troughs. Frequency - number of waves per second that pass through a given point (cycles/s, s-1, hz) The higher the number of waves, the higher the frequency. The higher the wave the higher the amplitude. Microwave oven excites the water molecules in food, creating kinetic energy which heats up the food. If a light shines on a metal, only some electrons come off. Current flows as soon as light of minimum frequency hits the metal. As the frequency of light hitting the metal increases, the higher the kinetic energy of the elec coming off (it increases linearly) Number of electrons increase with intensity of light, but not kinetic energy z) electrons.

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