Lab 9 - Atomic Spectra - Physics 8B Lab 9 Atomic Spectra...

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Physics 8B Lab 9 – Atomic Spectra rev 4.0 Lab 9 – Atomic Spectra Part 1: Predict λ th Emitted (from Energy Levels for Hydrogen) One of the great advances in understanding the behavior of matter was the discovery that the energy of an atom is quantized. This means that the binding energy of electrons in the atom can only have certain discrete values. The quantization of these energy levels is tied to the wave-like behavior of the particles in the atom. The simplest stable atom is that of hydrogen. The allowed energy levels of hydrogen are given by E n = " 13.6 eV n 2 where n can be any positive integer, and is called the principal quantum number . The possible energy levels of a hydrogen atom are shown below. E(eV) 0 n 6 5 4 -1.5 3 Paschen series -3.4 2 α β γ δ Balmer series -13.6 1 Lyman series
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Physics 8B Lab 9 – Atomic Spectra rev 4.0 Normally the hydrogen atom exists in its lowest energy state, called the ground state , i.e. n = 1. The energy required to free the electron completely is the energy required to increase the energy of the atom from the ground state up to 0eV, i.e. 13.6eV. This energy is called the ionization energy of hydrogen. A hydrogen atom may be excited to a higher state when an electron is shifted to an outer orbital. This could be initiated, for example, by the absorption of a photon or by a collision with a free electron. The atom will stay in the excited state for a short time, typically 10 -8 s. When the atomic electron drops back again to a lower orbital, a photon with energy E ph = hf = hc " is emitted. By conservation of energy, the energy of the photon emitted is equal to the energy change of the atom, i.e. E n i = E n f + E ph E ph = E n i " E n f hc = E n i # E n f where E n i and E n f are the energies of the initial and final states, respectively. As seen in the previous figure, there are many different jumps to lower energy levels that are possible. In hydrogen, only the jumps that finish at n = 2 may emit visible light. Even so, there are still many that finish at n f = 2. We will assume that all the light we will detect in this lab will correspond to jumps from n i = 7, 6, 5, 4, or 3 to n f = 2. a) Calculate the corresponding wavelengths for these jumps as predicted by this model? I.e. λ 7 2 , λ 6 2 . λ 5 2 , λ 4 2 , and λ 3 2 . b) and c) will show we can concentrate on the above transitions in today’s lab.
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Lab 9 - Atomic Spectra - Physics 8B Lab 9 Atomic Spectra...

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