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Atomic Spectroscopy Name______________________Objectivesexplain the difference between emission and absorption spectracalculate the energy of orbits in the Bohr model of hydrogencalculate E for energy transitions in the Bohr model of the hydrogen atomuse the equations =c/ and E=h to carry out necessary calculationsdemonstrate appropriate precautions in the use of high-voltage gas lampsrelate observed colors to regions of the electromagnetic spectrumIntroductionGaseous atoms and molecules may be converted to the plasma state by applying high voltages to samples in tubes. The color of these lamps is characteristic of the specific substance e.g. neon glows orange. The color we observe is a mixture of all of the wavelengths of radiation that are emitted. To observe individual colors of emission (emission spectra) a device is required that can separate this emitted light into a spectrum. One such device is a spectroscope. Another is a spectrophotometer. The spectroscope uses a prism and the colors are observed through an eyepiece. A spectrophotometer uses electronics and computer software to analyze and display the spectra.21336001251585The insight that Bohr presented to the scientific community was the recognition that the spectral lines could be connected to transitions of the electron from one orbit to another in the Bohr model of the atom. This simplified model of the atom is limited in its ability to predict spectral behavior but it is worthy of study because it works very well for hydrogen and assists beginning chemistry students in making connections between physical observations and atomic theory.Consider the following diagram:Notice that light is emitted asan electron moves from a higher energy orbit to a lowerenergy orbit. The energy of an orbit increases as a function of the distance from the nucleus.Note: the symbols f and are both used for frequency of light.Bohr developed an equation to calculate the energy levels of hydrogen:En = -2.178 E-18n2 (equation one)Energy is in joules and n is an integer from 1 to infinity - a quantum number.CalculationsFill out this table:Table 1. Hydrogen Energy Levelsn levelEnergy (Joules)123456∞0Plot these energy levels on a vertical scale on a separate piece of paper. (You can then take a picture and insert your photo into this document.)Notice that these energy levels are all negative numbers except the last one at n=infinity which is zero. This is because energy must be provided to the atom to move an electron which has a negative charge away from the nucleus which is positively charged. The most negative value of energy, the lowest in your diagram, is the one closest to the nucleus. Also notice that this is NOT a linear relationship. The energy levels are closer together as n increases. Your diagram must be labeled and have a shape something like this: Add diagram photo here.--------------------------------------------------------------------------------------------------------------------------------------Complete this table.Table 2. Spectral wavelengthsni=6ni=5ni=4ni=3ni=2|E| J nm|E| J nm|E| J nm|E| J nm|E| J nmnf=12.118E-1893.87nf=2nf=3nf=4nf=5nf=6Note: the subscripts i and f signify initial and final position of the electron so an electron that begins in level 6 and moves to level 1 emits a photon with a wavelength of 93.98 nm.Answer Questions1. What is the range in nanometers of the visible spectrum?2. Energy is _____________ when electrons move from higher levels to lower levels and _____________ when electrons move from lower levels to higher levels. 3. Ionization means an electron is completely removed from an atom. Complete removal occurs when n=infinity. How much energy would be required to ionize one atom hydrogen?4. How much energy in kJ would be required to ionize a mole of hydrogen atoms?Complete this tableTable 3. Hydrogen Spectral Line Assignmentwavelength (nm)assignment: ni nfregion of spectrum93.8761ultraviolet41ultraviolet52Notice all of the spectral lines that are in the visible region.Plot the wavelengths in table three as lines on a spectrum (the x axis is wavelength) and add color to match the color of the wavelengths. Your plot will look like the absorption spectrum below but with more lines. Insert a photo of your plot into this document here:-285750120650Answer Questions1. What is the Balmer series?2. What about other series for hydrogen - what are they called and what region of the electromagnetic spectrum would they occupy?3. Using the Internet research the spectra of several elements. How do the spectra of various elements compare? What are some dominant lines in these spectra? Which elements have more spectral lines?4. Why are the noble gases different colors when they are ionized by a high voltage?When you have completed this worksheet and inserted your photos – save this as a pdf file to submit. ................
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