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?

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

What is observed in a flame test with lithium?

Persistent golden-yellow flame Signup and view all the answers

What is the purpose of a flame in atomic spectroscopy?

To provide a high-temperature source of radiation Signup and view all the answers

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

The sample must be atomized in AAS Signup and view all the answers

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

To determine the elements present in a sample Signup and view all the answers

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

The pattern of lines in the spectra Signup and view all the answers

What is atomic spectroscopy used to determine?

The concentration of metallic atoms in a sample Signup and view all the answers

What is the primary difference between atomic and molecular spectra?

The number of transitions possible Signup and view all the answers

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

To convert the sample into a gaseous state Signup and view all the answers

What is a necessary condition for atomic spectroscopy?

A gaseous medium Signup and view all the answers

What is the process of generating atoms from molecules?

Atomization Signup and view all the answers

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

Only electronic Signup and view all the answers

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

To select a specific wavelength of radiation Signup and view all the answers

What is the purpose of the flame in atomic spectroscopy?

To atomize the sample Signup and view all the answers

What is the difference between AAS and AES methods?

AAS measures absorbed radiation, and AES measures emitted radiation 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?

Flame Spectroscopy Signup and view all the answers

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

To detect the radiation absorbed or emitted by the sample Signup and view all the answers

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

To excite the atoms Signup and view all the answers

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

Atomization Signup and view all the answers

What is the key difference between absorption and emission spectra?

The direction of energy transfer Signup and view all the answers

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

Gaseous phase Signup and view all the answers

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

An increase of 4% in the number of excited atoms Signup and view all the answers

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

To divide the sample solution into very fine droplets Signup and view all the answers

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

Atomization and excitation of the sample occur Signup and view all the answers

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

Below 20000 0K Signup and view all the answers

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

To produce the necessary heat for atomization and excitation Signup and view all the answers

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

To plot a graph of concentration vs absorbance Signup and view all the answers

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

An increase in the absorbance of the sample Signup and view all the answers

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

The sample is vaporized by the action of heat Signup and view all the answers

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

The elements occur above 25000 0K Signup and view all the answers

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

Combustion of fuel and evaporation of solvent occur 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?

Below 2000 0K Signup and view all the answers

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

To prepare a blank sample for zero absorbance Signup and view all the answers

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

To introduce the sample into the flame Signup and view all the answers

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

Oxidation of the analyte occurs 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.