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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

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Exciting Electrons

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

Click to see how electrons behave Parts of a Wave: Wavelength (-Lambda)

Horizontal distance from crest to crest Meters or nanometers are the unitsParts of a wave: Frequency ( Nu)cycles past a given point in a fixed amount of time Hz or s-1 are the unitsWavelength and frequency are inversely related.

Inverse RelationshipSpeed of Light RelationshipConstant (c) = 2.998 x 108 m/secc = 2.998 x 108 m/sec =

Example ProblemCalculate the frequency of light that has a wavelength of 4.25 x 10-9m. 7.1 x 10 16 /sec = c = 2.998 x 108 m/sec = 4.25 x 10 -9 m ()

Shorter frequency Longer frequencyWavelength and Light RelationshipWhen visible light passes through prism, it separates out into colors based on wavelength.

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

Energy of Photons RelationshipPlanks Constant (h) = 6.626 x 10 -34 J*s Energy of photons = Planks x frequencyE = h

E = 6.626 x 10 -34 J*s

Example ProblemCalculate 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) Atomic Emission Spectrumpassing electric current through gas in a tube energizes the electrons which emit light

each transition produces a line of specific wavelength in the spectrum

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