exciting electrons

Electrons as Waves of Energy

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

Click to see how electrons “behave”

Parts of a Wave: Wavelength (λ-Lambda)

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

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.

Inverse Relationship

Speed of Light Relationship

Constant (c) = 2.998 x 108

m/secc =

λ ν2.998 x 108 m/sec = λ ν

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)

Shorter frequency Longer frequency

Wavelength and Light Relationship

• When 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 Transition• This 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 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

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)

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