Presentation on theme: "THE DEVELOPMENT OF A NEW ATOMIC MODEL Honors Chemistry Section 4.1."— Presentation transcript:
THE DEVELOPMENT OF A NEW ATOMIC MODEL Honors Chemistry Section 4.1
Rutherford’s Atom Major Advance Did not explain all properties of the atom Proton-electron attraction Why didn’t atom collapse?
Light and Electrons Early 1900’s – light is a wave Visible Light – Electromagnetic Radiation Electromagnetic Spectrum
Electromagnetic Radiation Moves at speed of light (c) = 3.0 x 10 8 m/sec Wave Properties Frequency – ( 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.
Photoelectric Effect Early 1900’s This effect related to ν If wave this not the case Explained by Max Planck Planck studied emission of light from hot objects Said light emitted in small packets called quanta
Planck’s Equation E = hν h = 6.626 x 10 -34 Joules ･ seconds Joule – unit of energy E = Energy ν = frequency
Einstein Dual Wave-Particle nature of electromagnetic radiation Light can act both like a wave and like a stream of particles Particles called photons. Photon – particle of electromagnetic radiation with zero mass and carrying a quantum (packet) of energy Photoelectric 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
Photons Increase ν increase E Must have minimum ν to get minimum E Different metals require different minimum ν DEMO – Energy in Photons
Spectra Pass electricity through gas at low pressure – increase PE of gas Lowest energy state – ground state Higher PE state – excited state When an excited atom returns to ground state it releases energy as electromagnetic radiation