Presentation on theme: "Honors Chemistry Section 4.1"— Presentation transcript:
1Honors Chemistry Section 4.1 The Development of a new atomic model
2Rutherford’s Atom Major Advance Did not explain all properties of the atomProton-electron attractionWhy didn’t atom collapse?
3Light and Electrons Early 1900’s – light is a wave Visible Light – Electromagnetic RadiationElectromagnetic Spectrum
4Electromagnetic Radiation Moves at speed of light (c) = 3.0 x 108 m/secWave PropertiesFrequency – (ν) number of waves that pass a point in a given amount of time (cycles/sec, waves/sec, sec-1, Hertz)Wavelength – (λ) distance from a point on one wave to the same point on the next wave.
6Photoelectric Effect Early 1900’s This effect related to ν If wave this not the caseExplained by Max PlanckPlanck studied emission of light from hot objectsSaid light emitted in small packets called quanta
7Planck’s Equation E = hν h = 6.626 x 10-34 Joules ･seconds Joule – unit of energyE = Energyν = frequency
8Einstein Dual Wave-Particle nature of electromagnetic radiation Light can act both like a wave and like a stream of particlesParticles called photons.Photon – particle of electromagnetic radiation with zero mass and carrying a quantum (packet) of energyPhotoelectric effect – electromagnetic radiation only absorbed in whole numbers of photons.Eject an electron by hitting it with a photon with enough energy to free electron
9Photons Increase ν increase E Must have minimum ν to get minimum E Different metals require different minimum νDEMO – Energy in Photons
10SpectraPass electricity through gas at low pressure – increase PE of gasLowest energy state – ground stateHigher PE state – excited stateWhen an excited atom returns to ground state it releases energy as electromagnetic radiation