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Energy and Electrons Energy and Electrons

Energy and Electrons - PowerPoint Presentation

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Energy and Electrons - PPT Presentation

WaveParticle Duality JJ Thomson won the Nobel prize for describing the electron as a particle His son George Thomson won the Nobel prize for describing the wavelike nature of the electron The electron is a particle ID: 441449

light energy electron atom energy light atom electron frequency wave wavelength spectrum electromagnetic radiation atoms excited line 1011 units

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Slide1

Energy and ElectronsSlide2

Wave-Particle Duality

JJ Thomson won the Nobel prize for describing the electron as a particle.

His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron.

The electron is a particle!

The electron is an energy wave!Slide3

Confused??? You’ve Got Company!

“No familiar conceptions can be woven around the electron; something unknown is doing we don’t know what.”

Physicist Sir Arthur

Eddington

The Nature of the Physical World

1934Slide4

The Wave-like Electron

Louis

deBroglie

The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.Slide5

c =



C

= speed of light, a constant (3.00 x 108 m/s)

= frequency, in units of hertz (hz, sec-1)

= wavelength, in meters

Electromagnetic radiation propagates through space as a wave moving at the speed of light.Slide6

Types of electromagnetic radiation

:Slide7

Electromagnetic Radiation (Light) as a Key to Understanding Electron Paths

Early scientists discovered that Electromagnetic radiation (light) is given off by atoms of an element when they have been excited by some form of energy

Furthermore, atoms of different elements give off different colors of light when they are excited

.Slide8

When salts containing Li, Cu, and Na dissolved in methyl alcohol are set on fire, brilliant colors result.

Li

Cu

NaSlide9

Spectral Analysis of Emitted Light from Excited AtomsWhen the emitted light from excited atoms was passed through a prism, a curious spectrum of discrete lines of separate colors, separate energies, was observed rather than a continuous spectrum of

ROY G BIV

.Furthermore, different elements show totally different line spectra.In fact, line spectra are used to identify the presence of different elementsSlide10
Slide11

Interpretation of Atomic Spectra

The line spectrum must be related to energy transitions in the atom.

Absorption = atom gaining energy

Emission = atom releasing energy

Since all samples of an element give the exact same pattern of lines, every atom of that element must have only certain, identical energy statesThe energy of an atom is quantized – limited to discrete values

If the atom could have all possible energies, then the result would be a continuous spectrum instead of linesSlide12

Continuous Spectrum

Atomic Line Spectrum

NaSlide13

E = h

E

= Energy, in units of Joules (kg·m

2

/s2

)

h

= Planck’s constant (6.626 x 10-34 J·s)

= frequency, in units of hertz (

hz

, sec

-1

)

Max Planck

, a German Physicist, studied the emission of light by hot objects. He determined that there is a minimum amount of energy lost or gained by an atom, called a

quantum

of energy.

Energy EquationSlide14

Long

Wavelength

=

Low Frequency

= Low ENERGY

Short

Wavelength

= High Frequency =

High ENERGY

Wavelength TableSlide15

Calculating EnergyWhat is the energy of a photon of microwave radiation with a frequency of 3.20 x 1011 s-1 ?E = h

h = 6.626 x 10-34 J x s

 = 3.20 x 1011 s-1

E = (6.626 x 10-34 J x s)(3.20 x 1011

s-1)

E = 2.12 x 10-22 JSlide16

Calculating frequencyOrange light has a wavelength of 6.20 x 10-7 m. What is the frequency?

c

= speed of light = 3.00 x 10

8

m/s

 

3.0 x 10

8

m/s

6.2 x 10

-7

m

= 4.8

x 10

14

s

-1

=

 Slide17

Relating Frequency, Wavelength and Energy

Common re-arrangements: