1.1.1 Mass Spectrometer Flashcards
What is the mass spectrometer?
It is a machine that can analyse samples of elements. It will give you accurate information about which isotopes are in the sample, and their relative amounts.
Where is an example of somewhere that will carry a mass spectrometer?
Space probes carry mass spectrometers to analyse samples of the soil and atmospheric gases on other planets.
What state must a sample be to be injected into the mass spectrometer?
The sample must be in the gaseous state, so liquid or solid samples are heated to vaporize them.
What are the four main stages of mass spectroscopy?
Ionization, acceleration, deflection, and detection.
Why must the sample be ionized?
So that particles in the sample can be accelerated and deflected in the middle two stages. It also means that the particles can be detected in the last stage.
How is a sample ionized?
High-energy electrons stream off a hot metal wire in an electron gun. These electrons hit atoms in the sample and knock out electrons from them.
What do ionized samples become?
The conditions are adjusted so that only one electron is removed from each atom. This means that they become ions with single positive charges.
What is the general equation to show the process of ionization?
X(g) + e(-) –> X(+)(g) + 2e(-)
Why do the ions have to be accelerated?
So that they move through the mass spectrometer
How does acceleration occur?
This is done using an electric field. The ions are positively charged, so they are attracted to negatively charged plates and through narrow slits in them.
What two jobs does the acceleration stage do?
- It makes the ions in the sample move very quickly- It focuses the ions in a narrow beam
Why is the mass spectrometer connected to a vacuum pump?
The pump removes air from inside it. This stops molecules in the air getting in the way of speeding ions.
How does deflection work?
A magnetic field produces a force that pushes (deflects) the ions sideways.
What does the force of the magnetic field in deflection depend on?
The force depends only on the size of the charge on the ion.
What does the amount of deflection depend on?
If all the ions have one charge each, and are travelling at the same speed, the amount of deflection depends on the mass of the ions. Lighter ions will be deflected more than heavier ones.
