Isotope characteristics differ U 238 92 U 235 92.

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Isotope characteristics differ U 238 92 U 235 92

Binding energy Energy released when a nucleus is formed from protons and neutrons. Mass is lost. E = mc 2 –where m is the lost mass

The photon A “particle” of light A “quantum” of light energy The energy of a given photon depends on the frequency (color) of the light

But light is also a wave! Travels at constant speed c in a vacuum. c = f –c: 3 x 10 8 m/s –  wavelength (m) – f: frequency (Hz)

Calculating photon energy E = hf –E: energy (J or eV) –h: Planck’s constant 6.625  10 -34 J s or 4.14  10 -15 eV s –f: frequency of light (s -1, Hz)

The “electron-volt” (eV) is an energy unit Useful on the atomic level. If a moving electron is stopped by 1 V of electric potential, we say it has 1 electron-volt (or 1 eV) of kinetic energy!

Converting eV to Joules (J) 1 eV = 1.602  10 -19 J

Absorption Spectrum Photon is absorbed and excites atom to higher quantum energy state. 0 eV -10 eV hf Ground state EE

Absorption Spectrum Absorption spectra always involve atoms going up in energy level. 0 eV -10 eV ionized

Emission Spectrum Photon is emitted and atom drops to lower quantum energy state. 0 eV -10 eV hf Excited state EE

Emission Spectrum Emission spectra always involve atoms going down in energy level. 0 eV -10 eV ionized

Wavelength Photon –  = c/f Particle – = h/p – deBroglie wavelength

Compton Scattering Proof of the momentum of photons. High-energy photons collided with electrons. Conservation of momentum. Scattered photons examined to determine loss of momentum.

Davisson-Germer Experiement Verified that electrons have wave properties by proving that they diffract. Electron diffraction