The Bohr ModelNiels Bohr

Violet: nm Indigo: nm Blue: nm Green: nm Yellow: nm Orange: nm Red: nm

Electromagnetic Spectrum

Frequency-the number of wave cycles passing a point in a period of time. (C=3.00 x 10 8 m/s) As frequency increases, wavelength decreases crest trough

Yellow light given off by a sodium vapor lamp has a wavelength of 589 nm. What is the frequency of this radiation? v = c/λ v = c/λ = 3.0 x 10 8 m/s x 10 9 nm = 5.09x10 14 s -1 = 3.0 x 10 8 m/s x 10 9 nm = 5.09x10 14 s nm 1 m 589nm 1 m

Max Planck Planck stated energy can be released and absorbed in discrete packets called “quanta”. The energy of one quanta is E = h·ν Where h = 6.63 x J·s

Light of a particular wavelength (λ) has a particular frequency (v) and energy. Light of a particular wavelength (λ) has a particular frequency (v) and energy. E = h∙v and c = λ∙v E = h∙v and c = λ∙v c=3.00 x 10 8 m/s speed of light h=6.63 x joule-sec Plank’s constant

Calculate the energy of one photon of yellow light whose wavelength is 589nm. E = hv = (6.626 x J∙s)(5.09x10 14 s -1 ) = (6.626 x J∙s)(5.09x10 14 s -1 ) = 3.37 x J = 3.37 x J Substitute v= c/λ in E = h∙v and you get E = h∙c λ

Pop quiz What do the following symbols stand for? h 4. c 5. E Bonus: Write the two formulas using the above symbols frequency wavelength Planck’s constant Speed of light energy Hz, s -1, 1/s m, nm J∙s m/s J =c/v =c/v E=h∙v

Why each element produces a unique line spectra.

H Add energy (heat or electricity) Excited state

Wave-particle duality of light Planck stated that energy is radiated in discrete packets called quanta. Planck stated that energy is radiated in discrete packets called quanta. A photon is a quantum of light having the energy h∙v. A photon is a quantum of light having the energy h∙v. Light’s particle nature is seen in its ability to eject electrons from a surface (photoelectric effect), and by the emission spectra of elements. Light’s particle nature is seen in its ability to eject electrons from a surface (photoelectric effect), and by the emission spectra of elements.

Young woman or old woman? What do you see?

Light’s wave nature is seen by its ability to diffract, reflect, and refract. Light’s wave nature is seen by its ability to diffract, reflect, and refract.

Photoelectric effect A minimum amount of energy is needed to eject an electron from a surface exposed to light. A minimum amount of energy is needed to eject an electron from a surface exposed to light.

Summary: Bohr Model of the Atom What works? Shows that Electron Energies are Quantized Applications: “Neon” lights fireworks Auroras fluorescence spectroscopy chemiluminescence bioluminescence