Arrangement of Electrons in Atoms The Development of a New Atomic Model - 4.1

The Old Atomic Model Problem with Rutherford model – no explanation of where e-s are New info about light led to new model of the atom Before 1900 scientists thought light traveled like a wave. We know now that light behaves like a wave and like a particle

The Wave Description Called the dual wave-particle nature of light! Electromagnetic Radiation - form of E that exhibits wavelike behavior as it travels thru space Electromagnetic Spectrum - all of the forms of electromagnetic radiation (visible light, x-rays, uv and infrared light, micro and radio waves)

The Wave Description All types of emag rad. move at 3.00 x 108 m/s in a vacuum. (slightly slower thru matter) This is the speed of light

The Electromagnetic Spectrum

Wavelength and Frequency Wavelength - λ the distance between corresponding pts on adjacent waves Frequency - ν the number of waves that pass agiven point in a specific time, usually 1 second Frequency is expressed in Hertz (Hz)

The Relationship B/T Freq. and Wavelength c = λν The speed of light = wavelength times frequency The wavelength of red light is 7.6 x 10-7 m, calculate the frequency. F = speed      =  2.998 x 108 m/s wavelength            7.6 x 10-7 m Frequency = 3.9 x 1014Hz

The Photo-electric Effect The emission of e-s from a metal when light shines on the metal Light had to be a certain freq. to emit e-s

The Particle Description of Light Planck proposed idea of quanta (E packets) Quantum of energy - the minimum quantity of E that can be lost or gained by an atom

The Particle Description of Light E = hν Where E is the energy in joules of a quantum of radiation υ is the frequency in s-1 h is Planck's constant of 6.626 x 10-34 J *  s

Einstein and the dual particle-wave nature Ein. supported Planck by proposing the duality of light as particle and wave Ein. proposed particles of light carry a quantum of E called photons (0 mass)

Einstein and the dual particle-wave nature The E of a photon depends on the υ of rad. E absorbed in whole # of photons Different metals need diff. υ to remove an e-

The Line Emission Spectrum LES = the result from a narrow beam of the emitted light that is shined through a prism when it separated into colors of the visible spectrum The Continuous Spectrum

The H atom and the LES Electric current passed thru a gas at a low pressure

E Levels Ground state - the lowest E level of an atom (very stable level) Excited state - a state in which an atom has a higher potential E than it has in its ground state

E Levels When an e- falls from the excited state, a photon is given off - the E of the photon is = to the E difference H only emits certain freq. so e- exists in specific E levels