72 and 73 quantum effects and photons bohrs atomic

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7.2 and 7.3 Quantum effects and photons / Bohr’s atomic theory Experiments on the photoelectric effect have lead to today’s accepted theory of atoms. The photoelectric effect = electrons are ejected from the surface of a metal when a certain frequency of light shines on its surface.
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- High E light causes K metal to emit electrons. E is absorbed by K in the form of light and released in the form of electricity (ejecting electrons). The light absorbed and the electron must have the same E! E = hν ν electron = ν photon - The electrons in a particular atom are placed in orbitals of different energy (E) levels. When an atom absorbs E, the electrons in those E levels become excited and transition to a higher, discrete energy level. - A particular atom always has a characteristic emission of EM radiation called a line spectrum . Astronomers use this information to determine the atmospheric composition of other planets. Bohr’s Postulates 1. Energy Levels : an electron in an atom can have only specific (quantized) energy values. 2. Transitions : An electron in an atom can change energy only by going from one E level to another E level (and never in between). By changing E levels, an electron undergoes a transition. 7.4 Quantum Mechanics -Both electrons and light have wave and particle light behavior. λ = h/mν m = momentum wave functions = mathematically describe the wave properties of subatomic particles. It describes cyclical behavior. The uncertainty principle : states that the exact position and momentum of an electron cannor be measured at the same time. Therefore we cannot know exactly where an electron is around the nucleus but we can estimate it (probability).
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