Atomic Spectroscopy Quiz
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Questions and Answers

What is the principle behind atomic absorption spectroscopy?

  • Ionization of atoms in a high-temperature flame
  • Absorption of radiation to excite electrons (correct)
  • Chemical reaction between elements in a flame
  • Emission of radiation to return electrons to a lower energy state

    • What is observed in a flame test with calcium?

  • Violet flame
  • Yellowish-green flame
  • Brick-red flame (correct)
  • Crimson flame

    • Why do different atoms absorb or emit different wavelengths of light?

  • Due to differences in chemical reactivity
  • Due to differences in atomic mass
  • Due to differences in thermal conductivity
  • Due to differences in electron energy levels (correct)

    • What is the process in atomic emission spectroscopy?

    <p>Emission of radiation as electrons return to a lower energy state</p> Signup and view all the answers

    What is observed in a flame test with lithium?

    <p>Persistent golden-yellow flame</p> Signup and view all the answers

    What is the purpose of a flame in atomic spectroscopy?

    <p>To provide a high-temperature source of radiation</p> Signup and view all the answers

    What is the primary difference between Atomic Absorption Spectroscopy (AAS) and UV-visible absorption spectrophotometry?

    <p>The sample must be atomized in AAS</p> Signup and view all the answers

    What is the purpose of Atomic Absorption Spectroscopy (AAS)?

    <p>To determine the elements present in a sample</p> Signup and view all the answers

    What is the key characteristic of atomic spectra that provides specificity?

    <p>The pattern of lines in the spectra</p> Signup and view all the answers

    What is atomic spectroscopy used to determine?

    <p>The concentration of metallic atoms in a sample</p> Signup and view all the answers

    What is the primary difference between atomic and molecular spectra?

    <p>The number of transitions possible</p> Signup and view all the answers

    What is the purpose of the atomization step in AAS and AES?

    <p>To convert the sample into a gaseous state</p> Signup and view all the answers

    What is a necessary condition for atomic spectroscopy?

    <p>A gaseous medium</p> Signup and view all the answers

    What is the process of generating atoms from molecules?

    <p>Atomization</p> Signup and view all the answers

    What is the type of transition that occurs in atomic spectra?

    <p>Only electronic</p> Signup and view all the answers

    What is the role of the monochromator in AAS and AES instruments?

    <p>To select a specific wavelength of radiation</p> Signup and view all the answers

    What is the purpose of the flame in atomic spectroscopy?

    <p>To atomize the sample</p> Signup and view all the answers

    What is the difference between AAS and AES methods?

    <p>AAS measures absorbed radiation, and AES measures emitted radiation</p> Signup and view all the answers

    What is the study of absorption and emission of electromagnetic radiation by monatomic particles in a gaseous state called?

    <p>Flame Spectroscopy</p> Signup and view all the answers

    What is the purpose of the detector in AAS and AES instruments?

    <p>To detect the radiation absorbed or emitted by the sample</p> Signup and view all the answers

    What is the purpose of the external light source in atomic spectroscopy?

    <p>To excite the atoms</p> Signup and view all the answers

    What is the necessary step after sample preparation in atomic spectroscopy?

    <p>Atomization</p> Signup and view all the answers

    What is the key difference between absorption and emission spectra?

    <p>The direction of energy transfer</p> Signup and view all the answers

    What is the phase of the sample required for atomic spectroscopy?

    <p>Gaseous phase</p> Signup and view all the answers

    What is the result of a 10°C increase in flame temperature?

    <p>An increase of 4% in the number of excited atoms</p> Signup and view all the answers

    What is the primary function of the nebulizer in a flame atomizer?

    <p>To divide the sample solution into very fine droplets</p> Signup and view all the answers

    What is the primary function of the interzonal region in the flame?

    <p>Atomization and excitation of the sample occur</p> Signup and view all the answers

    What is the approximate temperature range required for the atomization of potassium, sodium, lithium, and calcium?

    <p>Below 20000 0K</p> Signup and view all the answers

    What is the primary function of the burner in a flame atomizer?

    <p>To produce the necessary heat for atomization and excitation</p> Signup and view all the answers

    What is the purpose of preparing a series of standard solutions in the calibration curve method?

    <p>To plot a graph of concentration vs absorbance</p> Signup and view all the answers

    What is the result of spiking a sample in the standard addition method?

    <p>An increase in the absorbance of the sample</p> Signup and view all the answers

    What is the result of heating the sample in a flameless atomizer?

    <p>The sample is vaporized by the action of heat</p> Signup and view all the answers

    What is the outcome of ionization of potassium, sodium, lithium, and calcium?

    <p>The elements occur above 25000 0K</p> Signup and view all the answers

    What is the significance of the primary combustion zone in the flame?

    <p>Combustion of fuel and evaporation of solvent occur</p> Signup and view all the answers

    What is the temperature range of a flame produced by a mixture of natural gas or propane or butane with air?

    <p>Below 2000 0K</p> Signup and view all the answers

    What is the purpose of adjusting zero absorbance in the calibration curve method?

    <p>To prepare a blank sample for zero absorbance</p> Signup and view all the answers

    What is the role of the nebulization process in the flame atomizer?

    <p>To introduce the sample into the flame</p> Signup and view all the answers

    What is the significance of the secondary combustion zone in the flame?

    <p>Oxidation of the analyte occurs</p> Signup and view all the answers

    Study Notes

    Atomic Spectroscopy (AS)

    • Atomic Spectroscopy is a technique used to determine the concentration of metallic atoms in a sample.
    • Elements detectable by atomic absorption are highlighted in pink in the periodic table.

    Flame Test

    • A qualitative method used to identify certain elements.
    • The flame is used as a source of radiation.
    • Different elements produce distinct flame colors:
      • Sodium: golden-yellow
      • Lithium: carmine-red
      • Calcium: brick-red
      • Strontium: crimson
      • Barium, molybdenum, cesium: yellowish-green
      • Borates, copper, thallium: green
      • Lead, arsenic, antimony, bismuth, copper: blue

    Atomic Emission Spectroscopy (AES)

    • Atomic emission occurs when a valence electron in a higher energy atomic orbital returns to a lower energy atomic orbital.
    • Different atoms absorb/emit different wavelengths of light due to different energy transition levels.

    Atomic Absorption Spectroscopy (AAS)

    • A method that uses the absorption of light to determine elements in a sample.
    • The sample must be atomized.

    Fundamentals of AAS & AES

    • Absorption and emission of light by atoms is associated with transitions of electrons between different energy levels.
    • Atomic spectra: line spectra provide specificity; each element has its own pattern due to its unique electronic configuration.
    • Molecules have bonds, undergo rotational + vibrational + electronic transitions, resulting in a band spectrum, whereas atoms have only electronic transitions, resulting in a line spectrum.

    Instrument Components

    • UV-Vis Spectrometer:
      • Light source
      • Monochromator
      • Sample
      • Detector
      • Read-out/Data system
    • AAS Spectrometer:
      • Light source (particular wavelength)
      • Atomization (flame)
      • Sample
      • Monochromator
      • Detector
      • Read-out/Data system
    • AES Spectrometer:
      • Atomization (flame)
      • Sample
      • Monochromator
      • Detector
      • Read-out/Data system

    Flame Spectroscopy

    • The study of absorption/emission of electromagnetic radiation by monatomic particles in a gaseous state present in a flame.
    • Crucial steps in atomic spectroscopies:
      1. Atomization
      2. Excitation (specific λ)
      3. Emission (AES) or Absorption (AAS)

    General Principle of Flame Atomizer

    • Liquid samples are aspirated into the flame, breaking molecular bonds and producing free atoms.
    • The atomizer consists of a nebulizer and burner.

    Flame Atomizer Components

    • Nebulizer: divides the sample solution into fine droplets, which are aspirated into a fine spray or aerosol.
    • Burner: produces the necessary heat for atomization and excitation, with a temperature dependent on the fuel-oxidant ratio and type.

    Conditions for Flame Atomizer

    • Temperature: below 2000 K for potassium, sodium, lithium, and calcium; above 2000 K for ionization.
    • Dimensions and position of the burner and nebulization.
    • Rate of introduction of the sample to the flame.

    Quantitative Application

    • Calibration curve method:
      1. Choose a suitable lamp.
      2. Prepare standard solutions of the metal to be determined.
      3. Measure absorbance for each standard solution.
      4. Plot a graph representing concentration vs absorbance.
      5. Spray the sample and measure absorbance to determine concentration from the graph.
    • Standard addition method (spiking):
      1. Prepare a standard solution of exact and known concentration.
      2. Prepare a spiked sample by adding the standard solution to the unknown solution.
      3. Measure absorbance for the sample and spiked sample to determine concentration.

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    Description

    This quiz covers the basics of atomic spectroscopy, including atomic absorption and emission spectroscopy, flame tests, and qualitative analysis.

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