Atomic Absorption and Emission Theory
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Questions and Answers

Which element produces a carmine-red flame when heated?

  • Barium
  • Calcium
  • Lithium (correct)
  • Potassium

What happens when an electron transitions from a higher energy level to a lower one?

  • A photon is absorbed
  • Energy increases
  • A photon is emitted (correct)
  • The electron remains in the same orbital

Which of the following represents the energy of a photon emitted or absorbed during an electronic transition?

  • E = mv^2
  • E = K + U
  • E = hf (correct)
  • E = mc^2

In the Bohr model, what does a photon represent?

<p>A transition between orbitals (A)</p> Signup and view all the answers

What is the color of the flame produced by sodium?

<p>Golden-yellow (D)</p> Signup and view all the answers

Which element is associated with producing a green flame?

<p>Copper (D)</p> Signup and view all the answers

According to the Bohr model, electrons are found in:

<p>Discrete orbitals (D)</p> Signup and view all the answers

What effect does the transition from n = 1 to n = 2 have on an electron?

<p>It absorbs a photon (D)</p> Signup and view all the answers

What is the result of the transition from a higher energy level to a lower energy level in atomic emission?

<p>Emission of light (A)</p> Signup and view all the answers

What does the term 'quantization of energy' imply in atomic spectra?

<p>Only specific energy levels are allowed. (B)</p> Signup and view all the answers

How does absorbance relate to concentration in quantitative analysis?

<p>Absorbance is directly proportional to concentration. (D)</p> Signup and view all the answers

What does each element's unique emission line spectrum represent?

<p>Its unique atomic fingerprint. (A)</p> Signup and view all the answers

What is indicated by the intensity of an emission line in atomic spectra?

<p>Probability of electronic decay. (B)</p> Signup and view all the answers

In flame spectroscopy, what does a higher intensity of the emission spectrum indicate?

<p>Higher concentration of the analyte. (B)</p> Signup and view all the answers

Which relationship is correct regarding emission intensity and concentration?

<p>Emission intensity is directly proportional to concentration. (A)</p> Signup and view all the answers

What is the consequence of nuclear charge and orbital shape on atomic transitions?

<p>They determine the likelihood of specific transitions. (B)</p> Signup and view all the answers

What type of atoms can be analyzed through atomic absorption spectroscopy?

<p>Atoms of metals and their ions (B)</p> Signup and view all the answers

Which type of radiation is primarily used in atomic absorption and emission spectroscopy?

<p>UV and visible radiation (C)</p> Signup and view all the answers

What is the main difference between atomic absorption and atomic emission spectroscopy?

<p>AAS quantifies ground state metal atoms while AES quantifies excited state metal atoms. (A)</p> Signup and view all the answers

What type of information does a unique spectrum of an analyte provide in spectroscopy?

<p>Qualitative identification of the element (B)</p> Signup and view all the answers

Which of the following statements about the electronic transition in atomic absorption/emission spectroscopy is correct?

<p>Promoted electrons eventually decay to intermediate or ground state levels. (B)</p> Signup and view all the answers

Which of the following is an application of atomic absorption spectroscopy?

<p>To detect metal elements in aqueous solutions (C)</p> Signup and view all the answers

Atomic emission spectroscopy primarily measures what type of process?

<p>Emission of light from excited atoms (C)</p> Signup and view all the answers

What does the plot of instrumental response vs. concentration indicate in quantitative analysis?

<p>Correlation between concentration and measured absorbance or emission (D)</p> Signup and view all the answers

What is the ground state electron configuration for sodium (Na)?

<p>[Ne]3s1 (D)</p> Signup and view all the answers

What is the primary characteristic of the ground state of an atom?

<p>It is the most stable arrangement of electrons. (D)</p> Signup and view all the answers

In which of the following scenarios will an atom experience an excited state?

<p>Absorption of quantized energy. (D)</p> Signup and view all the answers

How many electrons can occupy a single atomic orbital?

<p>Two electrons of opposite spin. (D)</p> Signup and view all the answers

Which of the following orbital configurations corresponds to an excited state of calcium (Ca)?

<p>[Ar]4s14p1 (D)</p> Signup and view all the answers

What is the outcome when an electron transitions from a higher energy level to a lower energy level in an atom?

<p>Energy is released. (D)</p> Signup and view all the answers

Which principal components are required for an atomic absorption spectrometer?

<p>Radiation source, hollow cathode lamp, optical filter, and detector. (D)</p> Signup and view all the answers

What is the relationship between wavelength and the energy of absorbed radiation in atomic electron transitions?

<p>Shorter wavelengths correspond to higher energy. (D)</p> Signup and view all the answers

What is the first step that occurs when an analyte species is aspirated into the flame?

<p>Conversion of metal ions to gaseous atoms (D)</p> Signup and view all the answers

In Atomic Absorption Spectroscopy (AAS), what does 'A' represent in the equation A = abc?

<p>Absorbance of the analyte (B)</p> Signup and view all the answers

Which equation best represents the relationship in Atomic Emission Spectroscopy (AES)?

<p>IE = m C + b (A)</p> Signup and view all the answers

What is required to promote valence electrons to higher energy orbitals in AAS?

<p>Radiation from a hollow cathode lamp (C)</p> Signup and view all the answers

In the process of excitation in AES, what type of energy is used?

<p>Thermal energy (B)</p> Signup and view all the answers

What is the significance of λmax in the absorption measurement process?

<p>It is the wavelength at which absorbance is highest (B)</p> Signup and view all the answers

What is the primary mechanism measured in Atomic Absorption Spectroscopy (AAS)?

<p>Absorption by ground state gaseous metal atoms (D)</p> Signup and view all the answers

What happens to analyte ions during the second experimental step?

<p>They are excited to higher energy states (B)</p> Signup and view all the answers

Which of the following statements correctly describes the detection limits of Atomic Emission Spectroscopy (AES)?

<p>Detection limits depend on the analyte. (A)</p> Signup and view all the answers

What type of radiation source is used in Atomic Absorption Spectroscopy (AAS)?

<p>Hollow Cathode Lamp (B)</p> Signup and view all the answers

Which of the following statements is true about the characteristics of absorbance measurement?

<p>It corresponds to the energy equivalent of the light absorbed (A)</p> Signup and view all the answers

What is one of the advantages of Atomic Absorption Spectroscopy (AAS) compared to Atomic Emission Spectroscopy (AES)?

<p>Higher selectivity (C)</p> Signup and view all the answers

In the process of atomization from Mn+(aq) to gaseous Mn, which energy source is primarily utilized in AAS?

<p>Thermal energy/Reducing species of the flame (B)</p> Signup and view all the answers

What distinguishes the measurement process in Atomic Emission Spectroscopy (AES) from that in Atomic Absorption Spectroscopy (AAS)?

<p>AES measures emission from excited state atoms. (A)</p> Signup and view all the answers

What order of magnitude is typically expected for the linear dynamic range (LDR) in analytical techniques discussed?

<p>3-5 orders of magnitude (B)</p> Signup and view all the answers

Which process is involved in converting an analyte metal species from aqueous ion to gaseous atom?

<p>Atomization and excitation (D)</p> Signup and view all the answers

Flashcards

Atomic Absorption Spectroscopy (AAS)

A technique that measures the absorption of light by ground state metal atoms in the gaseous state.

Atomic Emission Spectroscopy (AES)

A technique that measures the emission of light by excited state metal atoms in the gaseous state.

Analyte type (AAS/AES)

Metals (e.g., Cu, Fe) and metal ions (e.g., Cu2+, Fe2+).

Radiation types (AAS/AES)

Ultraviolet (180-380 nm) and visible light (380-780 nm).

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Measured process (AAS/AES)

Absorption (AAS), Emission (AES), or Fluorescence (AFS)

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Transition type (AAS/AES)

Electronic transition of valence electrons to higher energy levels, then back down.

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Qualitative analysis (AAS/AES)

Identifying elements using unique spectral patterns.

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Quantitative analysis (AAS/AES)

Determining the amount of an element.

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Atomic Emission Spectroscopy

A technique that measures light emitted by atoms when they return to a lower energy state.

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Emission (AES)

The process where excited atoms release energy as light when returning to the ground state

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Qualitative Data (AES)

Using the unique line spectrum to identify elements.

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Quantitative Data (AES)

Determining the amount of an element based on the intensity of its emitted light.

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Atomic Emission Spectra

The unique pattern of light emitted by an element's atoms.

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Emission Line

A specific wavelength of light emitted during a transition between energy levels in an atom.

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Quantization of Energy

Atoms can only absorb or emit specific amounts of energy in discrete amounts

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Flame Spectroscopy

A method for analyzing the emission spectrum of atoms using a flame to excite them.

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AAS Equation

Absorbance (A) of the analyte is directly proportional to its concentration (C) and the path length (b) of the light through the sample. A = abc.

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AAS Calibration Curve

A graph showing absorbance vs. analyte concentration used to determine the concentration of an unknown sample.

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Analyte Conversion (AAS/AES)

To analyze the analyte in AAS/AES, it must be converted from a chemical compound in solution (e.g. solvated ions to free gaseous atoms).

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Excitation to Higher Energy State (AAS/AES)

Atoms absorb energy from a light source (AAS) or temperature (AES) to reach excited electronic states.

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AAS Energy Source

The energy source for AAS is a hollow cathode lamp providing light of a specific wavelength (λ) to excite atoms.

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AES Energy Source

The energy source for AES is the flame or plasma, using thermal energy to excite atoms to higher states.

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Calibration Curve Equation (AAS)

The calibration curve equation (in AAS) using absorbance(A) = mC + b where m is the slope, and b is the y-intercept.

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λmax (Resonance Wavelength)

The wavelength at which maximum absorption or emission occurs in the spectrum.

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Electron configuration

The arrangement of electrons in the different energy levels and sublevels of an atom.

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Ground state

The lowest energy state of an atom, where electrons occupy the lowest available energy levels.

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Flame Test

A qualitative method used to identify metal ions by observing the color of the flame they produce when heated.

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Excited state

A state of an atom with electrons in higher energy levels than in the ground state, caused by energy absorption.

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Sodium Flame Color

Sodium produces a golden-yellow flame.

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Atomic orbital

A specific region around the nucleus where an electron is likely to be found.

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Valence electron

Electrons located in the outermost energy levels of an atom, involved in chemical reactions.

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Electronic Transition

Movement of an electron between different energy levels in an atom.

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Absorption of Photon

When an electron absorbs a photon (light particle), it jumps to a higher energy level.

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s, p, d, f orbitals

Different shapes of regions where electrons can be found around the atomic nucleus.

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Absorption of radiation

Process by which an atom gains energy from light or other electromagnetic radiation. The atom absorbs the energy, and the electron jumps to a higher energy level.

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Emission of Photon

When an electron moves to a lower energy level, it releases a photon.

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Line spectrum

A spectrum showing specific wavelengths of light emitted or absorbed by an atom. Each element has a unique line spectrum.

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Energy Level Diagram

A diagram used to represent the energy levels of an atom.

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Atomic Orbital

A three-dimensional region around the nucleus where an electron is likely to be found.

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Bohr Model

A model of the atom proposed by Niels Bohr in 1913, describing electrons orbiting the nucleus in discrete energy levels.

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Atom Cell

A device to convert analyte metal ions from an aqueous solution to gaseous atoms.

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Monochromator

Part of a spectrometer that selects a specific wavelength of light.

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Detection Limit (LOD)

The lowest concentration of an analyte that can be detected.

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Hollow Cathode Lamp

A light source used in AAS to excite atoms.

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Single Beam Spectrometer

Spectrometer using a single path for light.

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Double Beam Spectrometer

Spectrometer using two paths for light.

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Study Notes

Atomic Absorption and Emission Theory

  • Atomic absorption spectroscopy (AAS) measures the light absorbed by ground-state metal atoms in the gaseous state (M° (g)).
  • Atomic emission spectroscopy (AES) measures the light emitted by excited-state metal atoms in the gaseous state (M* (g)).
  • Analytes include atoms and ions of metals (e.g., Cu, Fe, Cu²⁺, Fe²⁺).
  • Elements detectable by AAS are highlighted in a periodic table.
  • AAS and AES can perform qualitative and quantitative analysis (ppm/ppb) of over 70 elements, making AAS a common metal analysis technique.
  • Types of radiation used include UV (180-380 nm) and visible light (380-780 nm). Interactions with metals affect valence electron distribution.
  • Processes measured include absorption, emission, and fluorescence.
  • Electronic transitions involve valence electrons being promoted to higher energy levels, and then falling back to lower energry levels (emission).
  • Qualitative analysis information from spectroscopy creates a fingerprint for an element through the element's unique spectrum.
    • This unique spectrum is plotted against wavelength for identifying elements.
  • Quantitative analysis is achieved by plotting instrumental response against analyte concentration.
    • AAS: Absorbance (A) is calculated using the equation A = abc, where 'a' is absorptivity, 'b' is path length and 'c' is concentration. Abs = mC+b.
    • AES: Emission Intensity (I) follows the equation I = mC+b.
  • Four major experimental steps include converting solvated ions to gaseous atoms, exciting atoms to higher energy levels, measuring absorption/emission , and extracting quantitative data.
  • In AAS, a hollow cathode lamp is used to excite atoms. In AES, thermal energy from a flame or plasma sources the atoms.
  • The Bohr model of an atom describes electrons orbiting the nucleus in discrete energy levels.
    • Electrons can only be in certain discrete orbits with particular energy levels.
    • Absorbing or emitting photons causes electrons to change orbitals.
    • The emitted or absorbed photon's energy is equal to the difference in energy between the two orbitals.
    • The calculated difference in energy levels (E) is related via the formula E = hf = hc/λ.
  • Electronic transitions occur when electrons move between orbitals.
    • Absorption involves the electron moving to a higher energy level.
    • Emission involves the electron returning to a lower energy level.
  • An electronic energy level diagram uses horizontal lines to show energy levels, increasing upward.
  • Quantum mechanics is used to find probabilities where electrons are likely to be found around the nucleus using orbitals (3-D maps).
    • Only 2 electrons of opposite spins can fit in an orbital..
  • Electronic configuration for an atom refers to the electrons' arrangement in different orbitals/subshells (s, p, d, f) and specifies the atom's unique arrangement, and ground state configuration is the lowest energy state.
  • Ground states as determined from the periodic table for elements such as Na and Ca are given.
  • Excited state configurations are presented for Na and Ca, and absorbed or emitted energy corresponds to specific transitions
  • The ground-state energy level diagram for Li. Diagrams outlining and illustrating transition of electrons
  • The absorption line spectrum generated for Lithium atoms.

Instrumentation for Atomic Absorption/Emission Spectroscopy

  • AAS instruments typically consist of a radiation source (hollow cathode lamp), atomization compartment (atom cell), monochromator, and detector.
  • AES instruments often have a temperature source (flame or ICP), monochromator, and detector.
  • For comparison, AAS uses a radiation source, while AES does not.
  • The instrumental layout for a single-beam spectrometer is presented.
  • A double-beam atomic absorption spectrometer design is presented.

Comparing AAS and AES

  • AAS measures absorption of radiant energy whereas AES measures emission.
  • In AAS, energy from an external lamp is absorbed by ground-state atoms, promoting them to higher energy levels.
  • In AES, input energy elevates atoms to an excited state thus emitting light at a characteristic wavelength.
  • Analytical process details are outlined in a table format.

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Atomic Absorption and Emission Theory PDF

Description

Explore the principles of atomic absorption and emission spectroscopy in this quiz. Learn how these techniques measure metal atoms and ions in the gaseous state, and understand their applications in qualitative and quantitative analysis. Test your knowledge on the types of radiation used and the processes involved in spectroscopy.

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