Atomic Structure
- 1. The Wave Nature of LightAll forms of NRG/Light have characteristic wavelengths (λ) and frequency (υ).Inversely related λ υ = c (the speed of light)Light visible to the naked eye exists as a tiny portion of the electromagnetic spectrum
- 3. Max PlanckTransfer of energy was not continuousOnly came in certain values (quantized)ΔE = hνh = Planck’s constant = 6.626 x 10-34 JsPackets of energy (quantum
- 4. Albert EinsteinProposed that electromagnetic radiation was quantized and made up of a stream of particlesPhotonsThe dual nature of lightλ = h/mv (deBroglie equation)
- 5. Electrons as WavesLouis de Broglie~1924Louis de Broglie (1924)Applied wave-particle theory to electronselectrons exhibit wave propertiesQUANTIZED WAVELENGTHSStanding WaveSecond Harmonic or First OvertoneFundamental mode 200 150 100 50 0- 50-100-150-200 200 150 100 50 0- 50-100-150-200 200 150 100 50 0- 50-100-150-2000 50 100 150 2000 50 100 150 2000 50 100 150 200Adapted from work by Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 6. Electrons as WavesQUANTIZED WAVELENGTHSCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 7. Electrons as WavesELECTRONSVISIBLE LIGHTEvidence: DIFFRACTION PATTERNSCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chemDavis, Frey, Sarquis, Sarquis, Modern Chemistry2006, page 105
- 8. Spectrum Light is diffracted (bent) through different objectsHydrogen Spectra gave interesting results
- 9. Niels Bohr In the Bohr Model (1913) the neutrons and protons occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun.They are not confined to a planar orbit like the planets are.
- 10. Bohr ModelPlanetary modelAfter Rutherford’s discovery, Bohr proposed that electrons travel in definite orbits around the nucleus.
- 11. Bohr Cont.When the electrons are in their lowest possible NRG level, they are in their ground state. Electrons absorb NRG and go to a higher NRG level(Excited State)NRG (Light) is released when the electron jumps from a higher NRG level to a lower NRG level(Fluorescence)Constantly happening
- 12. An unsatisfactory model for the hydrogen atomAccording to classical physics, lightshould be emitted as the electron circles the nucleus. A loss of energywould cause the electron to be drawncloser to the nucleus and eventuallyspiral into it.Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 294
- 13. Quantum Mechanical ModelNiels Bohr &Albert Einstein Modern atomic theory describes the electronic structure of the atom as the probability of finding electrons within certain regions of space (orbitals).
- 14. Modern ViewThe atom is mostly empty spaceTwo regionsNucleus protons and neutronsElectron cloudregion where you might find an electron
- 15. Quantum MechanicsWerner Heisenberg~1926Heisenberg Uncertainty PrincipleImpossible to know both the velocity and position of an electron at the same timegMicroscopeElectron
- 16. Quantum MechanicsSchrödingerWave Equation(1926)finite # of solutions quantized energy levelsdefines probability of finding an electronErwin Schrodinger~1926Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 17. Quantum MechanicsOrbitalOrbital (“electron cloud”)Region in space where there is 90% probability of finding an electron90% probability offinding the electronElectron Probability vs. Distance403020Electron Probability (%)100100150200250500Distance from the Nucleus (pm)Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 18. Quantum NumbersUPPER LEVELFour Quantum Numbers:Specify the “address” of each electron in an atomCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 19. Quantum NumbersPrincipal Quantum Number( n)Angular Momentum Quantum #( l)Magnetic Quantum Number( ml)Spin Quantum Number( ms)
- 20. Quantum Numbers1. Principal Quantum Number( n)Energy levelSize of the orbitalIntegral values 1s2s3sCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 21. Quantum Numbersspdf2. Angular Momentum Quantum #( l)Energy sublevelShape of the orbitalCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 22. Angular Momentum Quantum #( l )Has integral values from 0 to n-1Related to the shape of the orbitall = 0 is called sl = 1 is called pl = 2 is called dl = 3 is called f
- 23. Shapes of s, p, and d-Orbitals
- 25. Quantum Numbers3. Magnetic Quantum Number( ml)Orientation of orbitalSpecifies the exact orbital within each sublevelHas values between l and -lCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
- 26. Quantum Numbers4. Spin Quantum Number( ms)Electron spin +½ or -½An orbital can hold 2 electrons that spin in opposite directions.Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem