CHY 183 Lecture Notes - Lecture 13: Emission Spectrum, Spectroscopy, Transition Metal

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ladylycium

28 Feb 2022

School

Ryerson University

Department

Chemistry

Course

CHY 183

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Document Summary

Trace elements: small quantities/concentrations of an element (<1%) Provide "invisible" markers that can establish source of material or provide additional points for comparison. Emission spectrograph: vaporizes samples by heating to a high temperature -> atoms achieve excited state -> excited atoms emit light. Emission spectrum: light emitted from a source and separated into its component colours/frequencies. Line spectrum: type of emission spectrum; shows series of lines separated by black areas; light separated into components. Can be matched line for line in a comparison between samples. Atom: nucleus (protons and neutrons) + electrons outside in electron orbitals. Orbitals associated energy level (definite amount of energy) Each elements = own set of characteristic energy levels varying in distances from the nucleus. B/c energy levels fixed, atom will absorb only a definite value of energy (heat/light) Absorbed energy pushes electrons into higher energy level orbitals; atom is now in excited state.

Related Questions

1)Anemission spectrometer is an instrument that separates light emittedfrom a source and produces a spectrum, similar to the way the prismseparated the light. Which type spectra described in the BackgroundInformation (continuous, emission, absorption) would you expect tobe produced when sunlight is directed through aspectrometer? Explain youranswer.

2)Which typeof spectrum (continuous, emission, absorption would you expect tobe produced when the light produced from an element heated in aflame is directed through an emissionspectrometer? Explain youranswer.

Scientists can analyze metals using the emission spectrumproduced when the sample is introduced into the flame of anemission spectrometer. The flame provides the energy to excite theelectrons of the metal atoms to higher energy states. When theelectrons return to the ground state, lines of characteristicwavelengths are produced. The lines in the emission spectrum arecharacteristic of the metal because each atom's ground-stateelectron configuration is unique.

Part A

The emission line used for zincdeterminations in atomic emission spectroscopy is 214 nm. Ifthere are 8.00

Use a ruler to calibrate the spectral limits in the figure above. In other words, what are the right and left limits in nm, and what is the equation that converts distance on this page in cm to spectral units of nm? This âcalibrationâ will help you with the next item.

Use the NIST Atomic Spectral Database to assign the three bright spectral lines in the hydrogen spectrum.

Abstract This physical chemistry laboratory exercise will have students work with provided emission spectra for several elements and data collected on the NIST Atomic Spectral Database. First, students will develop a method for calculating what wavelengths of visible light are associated with the most intense spectral lines in the provided visible emission spectra. Then, the NIST Atomic Spectral Database will be accessed in order to identify select properties associated with the four most intense spectral lines. Introduction The emission process can be described in two general parts. Initially, energy is absorbed by an atom, and its electrons can be moved into higher energy (excited) states from their ground state The excitedrelectrons then "relax" and drop back to their ground state. Energy lost during an electron's retaxation process is emitted as a photon. Recall that the energy of a photon is photon upper E lower Where Ephoton is the energy of the photon that is emitted when the emitter drops from an upper energy state to a lower energy state, h is Planck's constant, c is the speed of light, and v is the wavenumber. Remember that the length units should match for c and v This is a good time to revisit a few concepts. Atoms and molecules possess discrete energy levels their energy levels are quantized and not continuous. Using eq 7.1, it is possible to determine the energy associated with a specific excited state to ground state transition if we can determine the wavelength of emitted light. Also keep in mind that there are selection rules that limit the type of transitions we can expect to observe. All of these points are reflected in an elemental or ionic emission spectrum. The visible light spectrum falls within a fairly narrow range of wavelengths, from approximately 400 to 700 nm. Even so, discrete spectral lines are seen in each element's visible light emission spectrum. Each (take some time to reflect on why that would be), each element also has a unique emission spectrum. This provides a diagnostic tool for determining the composition of a sample. As an example, the elements present in celestial objects can be determined by the light that they produce line represents one possible transition. Since each element has unique energy levels Some of the transitions observed in this lab exercise involve d-orbitals. As such, a discussion regarding d-orbitals and related selection rules is necessary at this point. The first goal is to determine which character table should be used. Start by observing the shape and relative orientations of the d-orbitals. Refer to Figure 1 below

CHY 183 Lecture Notes - Lecture 13: Emission Spectrum, Spectroscopy, Transition Metal

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