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Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 130a

Refer to Figure 2.10 showing a schematic illustration of a mass spectrometer. (a) What is the purpose of bombarding the gaseous atoms with an electron beam?

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Understand the basic function of a mass spectrometer, which is to measure the masses of atoms or molecules in a sample.
Recognize that the sample introduced into the mass spectrometer is typically in gaseous form to ensure that the atoms or molecules are free to move and interact.
Identify that the electron beam in the mass spectrometer is used to ionize the gaseous atoms. Ionization involves removing one or more electrons from the atoms, thus converting them into positively charged ions.
Acknowledge that these ions are necessary for the subsequent steps in the mass spectrometry process, as only charged particles can be manipulated and detected using electric and magnetic fields.
Realize that by analyzing the behavior of these ions (such as their paths through magnetic and electric fields and their eventual detection), the mass spectrometer can determine the mass-to-charge ratio (m/z) of the ions, which helps in identifying the atomic or molecular masses.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionization

Ionization is the process of converting neutral atoms or molecules into charged ions by adding or removing charged particles, typically electrons. In mass spectrometry, bombarding gaseous atoms with an electron beam provides enough energy to eject electrons from these atoms, resulting in the formation of positive ions. This is a crucial step for analyzing the mass-to-charge ratio of the ions produced.
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Mass Spectrometry

Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. It involves ionizing chemical species and sorting the resulting ions based on their mass and charge. The data obtained allows for the identification and quantification of substances in a sample, making it a powerful tool in chemistry and biochemistry.
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Electron Beam

An electron beam is a stream of electrons that can be directed towards a target, such as gaseous atoms in a mass spectrometer. The high energy of the electrons in the beam facilitates the ionization of the atoms by providing the necessary energy to overcome the ionization energy barrier. This interaction is essential for generating ions that can be analyzed in the mass spectrometer.
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