Exciting Electrons

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Electrons as Waves of Energy Can electrons move between energy levels? How do we know?

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Exciting Electrons. Can electrons move between energy levels? How do we know?. Parts of a Wave: energy traveling through space!. Horizontal distance from crest to crest . Vertical distance from zero (node) to crest of wave. What about Frequency?. - PowerPoint PPT Presentation

Transcript of Exciting Electrons

Page 1: Exciting Electrons

Electrons as Waves of Energy

Can electrons move between energy levels?How do we know?

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Click to see how electrons “behave”

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Parts of a Wave: Wavelength (λ-Lambda)

• Horizontal distance from crest to crest • Meters or nanometers are the units

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Parts of a wave: Frequency (ν –Nu)• cycles past a given point in a fixed amount of time • Hz or s-1 are the units• Wavelength and frequency are inversely related.

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Inverse Relationship

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Speed of Light Relationship

Constant (c) = 2.998 x 108

m/secc =

λ ν2.998 x 108 m/sec = λ ν

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Example Problem• Calculate the frequency of light that has a

wavelength of 4.25 x 10-9m.

7.1 x 10 16 /sec =

c = λ ν2.998 x 108 m/sec = 4.25 x 10 -9 m (ν)

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Shorter frequency Longer frequency

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Wavelength and Light Relationship

• When visible light passes through prism, it separates out into colors based on wavelength.

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Electron TransitionWhen electrons move from higher to lower energy

levels, they release energy in the form of radiation …. sometimes in the visible spectrum.

Electron releases energy (photon).

Energy has a particular wavelength.

Wavelength may be part of the visible light spectrum.

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Electronic Transition• This energy emitted is called a quantum of energy (E). • ONLY emitted when electrons transitions downward.• This process is known as electronic transition.

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Energy of Photons Relationship

• Planks Constant (h) = 6.626 x 10 -34 J*s

Energy of photons = Planks x frequencyE = h

E = 6.626 x 10 -34 J*s

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Example Problem

• Calculate the energy of light that has a frequency of 1.5 x 1015 Hz. (Hz =sec-1)

E = 9.95 x 10-19 J

E = 6.626 x 10 -34 J*s E = 6.626 x 10 -34 J*s (1.5 x 1015 per sec)

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Atomic Emission Spectrum• passing electric current through gas in a tube energizes

the electrons which emit light

• each transition produces a line of specific wavelength in the spectrum