Prepared by Lawrence Kok Tutorial on Electromagnetic Radiation, Emission Line spectrum and Bohr Model.

Electromagnetic Spectrum Electromagnetic spectrum ranges from Radiowaves to Gamma waves. - Form of energy - Shorter wavelength -> Higher frequency -> Higher energy - Longer wavelength -> Lower frequency -> Lower energy

Electromagnetic Spectrum Electromagnetic spectrum ranges from Radiowaves to Gamma waves. - Form of energy - Shorter wavelength -> Higher frequency -> Higher energy - Longer wavelength -> Lower frequency -> Lower energy Inverse relationship between- λ and f Wavelength, λ - long  Frequency, f - low  Wavelength, λ - short  Frequency, f - high 

Electromagnetic Spectrum Electromagnetic spectrum ranges from Radiowaves to Gamma waves. - Form of energy - Shorter wavelength -> Higher frequency -> Higher energy - Longer wavelength -> Lower frequency -> Lower energy Electromagnetic radiation Travel at speed of light, c = fλ -> 3.0 x 10 8 m/s Light Particle – photon have energy given by -> E = hf Energy photon - proportional to frequency Inverse relationship between- λ and f Wavelength, λ - long  Frequency, f - low  Wavelength, λ - short  Frequency, f - high  Plank constant proportionality constant bet energy and freq Excellent video wave propagation Click here to view.here

Electromagnetic Wave propagation. Electromagnetic radiation Moving charges/particles through space Oscillating wave like property of electric and magnetic field Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation. Electromagnetic wave propagation Click here to view videohere

Electromagnetic Wave propagation. Wave Electromagnetic radiation Moving charges/particles through space Oscillating wave like property of electric and magnetic field Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation. Electromagnetic wave propagation wave Wave – wavelength and frequency - travel at speed of light Click here to view videohere

Electromagnetic Wave propagation. Wave Electromagnetic radiation Moving charges/particles through space Oscillating wave like property of electric and magnetic field Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation. Electromagnetic wave propagation wave Wave – wavelength and frequency - travel at speed of light Violet λ = 410nm Red f = c/λ = 3 x 10 8 /410 x = 7.31 x Hz E = hf = x x 7.31 x = 4.84 x J λ = 700nm f = c/λ = 3 x 10 8 /700 x = 4.28 x Hz E = hf = x x 4.28 x = 2.83 x J Click here to view videohere

Electromagnetic Wave propagation. Wave Electromagnetic radiation Moving charges/particles through space Oscillating wave like property of electric and magnetic field Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation. Click to view video -Wave-particle duality Is it a particle or Wave? wave Wave – wavelength and frequency - travel at speed of light

Electromagnetic Wave propagation. Wave Electromagnetic radiation Simulation on Electromagnetic Propagation Click here to view simulationhereClick here to view simulationhereClick here to view simulationhere Electromagnetic radiation Moving charges/particles through space Oscillating wave like property of electric and magnetic field Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation. Click to view video -Wave-particle duality Is it a particle or Wave? wave Wave – wavelength and frequency - travel at speed of light

Electromagnetic Wave Violet λ = 410nm Red f = c/λ = 3 x 10 8 /410 x = 7.31 x Hz λ = 700nm f = c/λ = 3 x 10 8 /700 x = 4.28 x Hz Wavelength – Distance bet two point with same phase, bet crest/troughs – unit nm Frequency – Number of cycle/repeat per unit time (cycles in 1 second) – unit Hz

Electromagnetic Wave Violet λ = 410nm Red f = c/λ = 3 x 10 8 /410 x = 7.31 x Hz λ = 700nm f = c/λ = 3 x 10 8 /700 x = 4.28 x Hz Which wave have higher frequency, if both have same speed reaching Y same time? Violet Y Red X Wavelength – Distance bet two point with same phase, bet crest/troughs – unit nm Frequency – Number of cycle/repeat per unit time (cycles in 1 second) – unit Hz

Electromagnetic Wave Violet λ = 410nm Red f = c/λ = 3 x 10 8 /410 x = 7.31 x Hz λ = 700nm f = c/λ = 3 x 10 8 /700 x = 4.28 x Hz Which wave have higher frequency, if both have same speed reaching Y same time? Violet Y Red X Wavelength – Distance bet two point with same phase, bet crest/troughs – unit nm Frequency – Number of cycle/repeat per unit time (cycles in 1 second) – unit Hz Click here on excellent video red /violet wavehere Light travel same speed Red flippers – long λ - less frequent Violet shoes – short λ - more frequent Click here to view video energy photonhere

Continuous Spectrum : Light spectrum with all wavelength/frequency Continuous Spectrum : Light spectrum with all wavelength/frequency Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Continuous Spectrum Vs Line Spectrum

Continuous Spectrum : Light spectrum with all wavelength/frequency Continuous Spectrum : Light spectrum with all wavelength/frequency Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Atomic Emission Ground state Excited state Electrons from excited state Emit radiation when drop to ground state Radiation emitted Emission Spectrum Continuous Spectrum Vs Line Spectrum

Continuous Spectrum : Light spectrum with all wavelength/frequency Continuous Spectrum : Light spectrum with all wavelength/frequency Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Emission Line Spectrum : Spectrum with discrete wavelength/ frequency Emitted when excited electrons drop from higher to lower energy level Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Absorption Line Spectrum : Spectrum with discrete wavelength/frequency Absorbed when ground state electrons are excited Atomic Emission Vs Atomic Absorption Spectroscopy Ground state Excited state Electrons from excited state Emit radiation when drop to ground state Radiation emitted Emission Spectrum Electrons from ground state Absorb radiation to excited state Electrons in excited state Radiation absorbed Continuous Spectrum Vs Line Spectrum

Line Emission Spectra for Hydrogen Energy supplied to atoms Electrons excited - ground to excited states Electrons exist fixed energy level (quantum) Electrons transition from higher to lower, emit energy of particular wavelength/frequency - photon Higher the energy level, smaller the difference in energy bet successive energy level. Spectrum converge (get closer) with increase freq. Lines spectrum converge- energy levels also converge Ionisation energy determined (Limit of convergence) UV region Lyman Series n=∞ → n= 1 UV region Lyman Series n=∞ → n= 1 Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 IR region Paschen Series n=∞ → n= 3 IR region Paschen Series n=∞ → n= 3 Line Emission Spectroscopy

Line Emission Spectra for Hydrogen Energy supplied to atoms Electrons excited - ground to excited states Electrons exist fixed energy level (quantum) Electrons transition from higher to lower, emit energy of particular wavelength/frequency - photon Higher the energy level, smaller the difference in energy bet successive energy level. Spectrum converge (get closer) with increase freq. Lines spectrum converge- energy levels also converge Ionisation energy determined (Limit of convergence) N = 3-2, 656nm N= nm N= nm N= nm Visible region- Balmer Series UV region Lyman Series n=∞ → n= 1 UV region Lyman Series n=∞ → n= 1 Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 IR region Paschen Series n=∞ → n= 3 IR region Paschen Series n=∞ → n= 3 Line Emission Spectra Energy supplied Electrons surround nucleus in allowed energy states (quantum) Excited electron return to lower energy level, photon with discrete energy/wavelength (colour) given out. Light pass through spectroscope (prism/diffraction grating) to separate out diff colours Line Emission Spectroscopy

Line Emission Spectra for Hydrogen Energy supplied to atoms Electrons excited - ground to excited states Electrons exist fixed energy level (quantum) Electrons transition from higher to lower, emit energy of particular wavelength/frequency - photon Higher the energy level, smaller the difference in energy bet successive energy level. Spectrum converge (get closer) with increase freq. Lines spectrum converge- energy levels also converge Ionisation energy determined (Limit of convergence) N = 3-2, 656nm N= nm N= nm N= nm Visible region- Balmer Series UV region Lyman Series n=∞ → n= 1 UV region Lyman Series n=∞ → n= 1 Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 IR region Paschen Series n=∞ → n= 3 IR region Paschen Series n=∞ → n= 3 Line Emission Spectra Energy supplied Electrons surround nucleus in allowed energy states (quantum) Excited electron return to lower energy level, photon with discrete energy/wavelength (colour) given out. Light pass through spectroscope (prism/diffraction grating) to separate out diff colours Click here to view videohereClick here to view videohere Videos on line emission Line Emission Spectroscopy

Ground state Excited state Hydrogen Emission Spectroscopy – Visible region (Balmer Series) Line Emission Spectra for Hydrogen Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= Click here for detail noteshere Click here video line emission spectrumhere

Ground state Excited state Hydrogen Emission Spectroscopy – Visible region (Balmer Series) Line Emission Spectra for Hydrogen Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 Hydrogen discharge tube Hydrogen Emission Spectroscopy Click here for detail noteshere Click here video line emission spectrumhere

Ground state Excited state Hydrogen Emission Spectroscopy – Visible region (Balmer Series) Line Emission Spectra for Hydrogen Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 Hydrogen discharge tube Hydrogen Emission Spectroscopy n = 3-2 n= 4-2n= 5-2 λ = 656nm f = c/λ = 3 x 10 8 /656 x = 4.57 x Hz E = hf = 6.62 x x 4.57 x = 3.03 x J λ = 434nmλ = 486nm f = c/λ = 3 x 10 8 /434 x = 6.90 x Hz E = hf = 6.62 x x 6.90 x = 4.56 x J More energetic violet lineLess energetic red line Click here for detail noteshere Click here video line emission spectrumhere

Bohr Model for Hydrogen Atom – Ionization Energy Niels Bohr Model (1913) Electrons orbit nucleus. Orbits with discrete energy levels – Quantized. Transition electron bet diff levels by absorb/emit radiation with frequency, f determined by energy diff bet levels -ΔE = hf Energy light emit/absorb equal to diff bet energy levels Electronic Transition bet levelsEnergy level Bohr Model

Bohr Model for Hydrogen Atom – Ionization Energy Niels Bohr Model (1913) Electrons orbit nucleus. Orbits with discrete energy levels – Quantized. Transition electron bet diff levels by absorb/emit radiation with frequency, f determined by energy diff bet levels -ΔE = hf Energy light emit/absorb equal to diff bet energy levels Electronic Transition bet levelsEnergy level Bohr Model ∞ Light emitted equal to difference bet energy levels, -ΔE = hf Plank equation Higher energy level n, smaller the difference in energy bet successive energy level. ΔE = hf Light energy - ΔE = hf Frequency = ΔE/h Ionization energy Transition electron from 1 ->∞ Light given off

Bohr Model for Hydrogen Atom – Ionization Energy Niels Bohr Model (1913) Electrons orbit nucleus. Orbits with discrete energy levels – Quantized. Transition electron bet diff levels by absorb/emit radiation with frequency, f determined by energy diff bet levels -ΔE = hf Energy light emit/absorb equal to diff bet energy levels Electronic Transition bet levelsEnergy level Bohr Model ∞ Light emitted equal to difference bet energy levels, -ΔE = hf Plank equation Ionisation energy determined (Limit of convergence) Line spectrum converge (get closer) with increase freq Higher energy level n, smaller the difference in energy bet successive energy level. Lines in spectrum converge- energy levels also converge Visible region Balmer Series n=∞ → n= 2 Visible region Balmer Series n=∞ → n= 2 Increase freq  UV region Lyman Series n=∞ → n= 1 UV region Lyman Series n=∞ → n= 1 ΔE = hf Light energy - ΔE = hf Frequency = ΔE/h Increase freq  Line spectrum converge (get closer) with increase freq Ionization energy Transition electron from 1 ->∞ line converge Light given off

Energy Level/Ionization Energy Calculation ∞ Formula - energy level, n (eV) 1 2 n = energy level Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Energy level, n= 2 = -13.6/n 2 = -13.6/2 2 = -3.4 eV Energy level, n= 3 = -13.6/n 2 = -13.6/3 2 = eV eV – 1.6 x J h = x Js constant

Energy Level/Ionization Energy Calculation ∞ Formula - energy level, n (eV) 1 2 n = energy level Lower energy level, n -more stable electron -more – ve (-13.6eV) -Less energetic Higher energy level, n -more unstable electron -More + ve ( less negative) -More energetic Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Energy level, n= 2 = -13.6/n 2 = -13.6/2 2 = -3.4 eV Energy level, n= 3 = -13.6/n 2 = -13.6/3 2 = eV eV – 1.6 x J h = x Js constant Ionization energy Transition electron from 1 ->∞

Energy Level/Ionization Energy Calculation ∞ Formula - energy level, n (eV) Energy difference bet level 3 to n = energy level Lower energy level, n -more stable electron -more – ve (-13.6eV) -Less energetic Higher energy level, n -more unstable electron -More + ve ( less negative) -More energetic Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Energy level, n= 2 = -13.6/n 2 = -13.6/2 2 = -3.4 eV Energy level, n= 3 = -13.6/n 2 = -13.6/3 2 = eV Energy difference, n= 3-2 = – (-3.4) eV = 1.89 eV = 1.89 x 1.6 x J = x J 1eV – 1.6 x J h = x Js Light energy - ΔE = hf Frequency, f = ΔE/h f = x /6.626 x = 4.56 x Hz λ = c/f = 3 x 10 8 /4.56 x = 657 x = 657nm Ionization energy Transition electron from 1 ->∞ constant Light given off

Ionization Energy for Hydrogen Atom ∞ Ionization energy Min energy to remove 1 mole electron from 1 mole of element in gaseous state M(g)  M + (g) + e 1 2 n = energy level Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Ionization energy Transition electron from 1 ->∞ Energy level, n= ∞ = -13.6/n 2 = -13.6/∞ = o eV ∞ Energy Absorb Light/photon ABSORB by electron electron

Ionization Energy for Hydrogen Atom ∞ Ionization energy Min energy to remove 1 mole electron from 1 mole of element in gaseous state M(g)  M + (g) + e 1 2 n = energy level Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Ionization energy Transition electron from 1 ->∞ Energy level, n= ∞ = -13.6/n 2 = -13.6/∞ = o eV ∞ Energy Absorb Energy difference, n= 1-> ∞ = 0 – (-13.6) eV = 13.6 eV = 13.6 x 1.6 x J = x J for 1 electron Energy absorb for 1 MOLE electron x J - 1 electron x x 6.02 x J - 1 mole -1309kJ mol -1 Light/photon ABSORB by electron electron

Ionization Energy for Hydrogen Atom ∞ Ionization energy Min energy to remove 1 mole electron from 1 mole of element in gaseous state M(g)  M + (g) + e Energy difference bet level 3 to n = energy level Energy level, n= 1 = -13.6/n 2 = -13.6/1 = eV Energy difference, n= 3-2 = – (-3.4) eV = 1.89 eV = 1.89 x 1.6 x J = x J Light energy - ΔE = hf Frequency, f = ΔE/h f = x /6.626 x = 4.56 x Hz λ = c/f = 3 x 10 8 /4.56 x = 657 x = 657nm Ionization energy Transition electron from 1 ->∞ Energy level, n= ∞ = -13.6/n 2 = -13.6/∞ = o eV ∞ Energy Absorb Energy difference, n= 1-> ∞ = 0 – (-13.6) eV = 13.6 eV = 13.6 x 1.6 x J = x J for 1 electron Energy absorb for 1 MOLE electron x J - 1 electron x x 6.02 x J - 1 mole -1309kJ mol -1 Light given off, electronic transition from high -> low level Energy Released Light/photon ABSORB by electron Light given off electron

Energy/Wavelength – Plank/Rydberg Equation ΔE = hf ∞ Formula – Plank Equation 1 2 n = energy level R = Rydberg constant R = x 10 7 m Rydberg Equation to find wavelength N f = final n level N i = initial n level ∞ Energy Level/Ionization Energy Calculation

Energy/Wavelength – Plank/Rydberg Equation ΔE = hf ∞ Formula – Plank Equation Electron transition from 3 -> n = energy level R = Rydberg constant R = x 10 7 m Rydberg Equation to find wavelength n f = 2, n i = 3 R = x 10 7 λ = 657 x = 657 nm N f = final n level N i = initial n level f = c/λ = 3 x 10 8 /657 x = 4.57 x Hz Energy photon- high -> low level ∞ Energy Level/Ionization Energy Calculation Light given off Rydberg Eqn find wavelength emit

Energy/Wavelength – Plank/Rydberg Equation ΔE = hf ∞ Formula – Plank Equation Electron transition from 3 -> n = energy level R = Rydberg constant R = x 10 7 m Rydberg Equation to find wavelength n f = 2, n i = 3 R = x 10 7 λ = 657 x = 657 nm N f = final n level N i = initial n level f = c/λ = 3 x 10 8 /657 x = 4.57 x Hz Energy photon- high -> low level Click here to view videohereClick here to view videohere Click here on energy calculationhere ∞ Energy Level/Ionization Energy Calculation Light given off Rydberg Eqn find wavelength emit

∞ Electron transition from 3 -> n = energy level n f = 2, n i = 3 R = x 10 7 λ = 657 x = 657 nm f = c/λ = 3 x 10 8 /657 x = 4.57 x Hz Energy photon- high -> low level ∞ Light given off, electronic transition from high -> low level Light given off Rydberg Eqn find wavelength emit

∞ Electron transition from 3 -> n = energy level n f = 2, n i = 3 R = x 10 7 λ = 657 x = 657 nm f = c/λ = 3 x 10 8 /657 x = 4.57 x Hz Energy photon- high -> low level ∞ Ionization Energy for Hydrogen Atom Ionization energy Min energy to remove 1 mole electron from 1 mole of element in gaseous state M(g)  M + (g) + e Ionization energy Transition electron from 1 -> ∞ Energy Absorb Rydberg Eqn find ionization energy n f = ∞, n i = 1 R = x 10 7 Light/photon ABSORB by electron electron Light given off, electronic transition from high -> low level Light given off Rydberg Eqn find wavelength emit

∞ Electron transition from 3 -> n = energy level n f = 2, n i = 3 R = x 10 7 λ = 657 x = 657 nm f = c/λ = 3 x 10 8 /657 x = 4.57 x Hz Energy photon- high -> low level ∞ Ionization Energy for Hydrogen Atom Ionization energy Min energy to remove 1 mole electron from 1 mole of element in gaseous state M(g)  M + (g) + e Ionization energy Transition electron from 1 -> ∞ Energy Absorb Rydberg Eqn find ionization energy n f = ∞, n i = 1 R = x 10 7 λ = 9.11 x Energy absorb for 1 MOLE electron x J - 1 electron x x 6.02 x J - 1 mole -1312kJ mol -1 Energy, E = hf = x x 3.29 x = x J for 1 electron f = c/λ = 3 x 10 8 /9.11 x = 3.29 x Hz Light/photon ABSORB by electron electron Light given off, electronic transition from high -> low level Light given off Rydberg Eqn find wavelength emit

Continuous Spectrum Light spectrum with all wavelength/frequency Emission Line Spectrum Spectrum with discrete wavelength/ frequency Excited electrons drop from higher to lower energy level Continuous Spectrum Vs Line Spectrum Click here spectrum for diff elementshereClick here spectrum for diff elementhereClick here on quantum mechanic, structure of atomhere Click here to view excellent simulationhereClick here to view simulationhere Excellent simulation on emission spectrum Emission line spectrum for different elements Click here to view simulationhere Video on quantum mechanics

Acknowledgements Thanks to source of pictures and video used in this presentation Thanks to Creative Commons for excellent contribution on licenses Prepared by Lawrence Kok Check out more video tutorials from my site and hope you enjoy this tutorial