Chemistry Unit 1

• The first function of a mass spectrometer is atomization which is the separation of a substance into atoms
• The second function of a mass spectrometer is ionization. The ions produced will always be positively charged, usually 1+
• The third function is acceleration. Ions are accelerated and separated according to their mass-to-charge ratio in a magnetic field
• The fourth function of a mass spectrometer is deflection. Charged particles get deflected by the magnetic field.
• The fifth function of a mass spectrometer is deflection. Deflected particles hit a detector which measures the number of particles and amount of deflection
• The 5 functions of a mass spectrometer are atomization, ionization, acceleration, deflection, and detection.
• When a sample enters a mass spectrometer the sample is vaporised and then ionised using high energy electrons. Next, they're accelerated and separated according to their mass-to-charge ratio in a magnetic field. Ions that have a particular mass-to-charge ratio are then detected by a device that counts the number of ions that strike it to produce a mass spectra.
• Relative atomic mass is the average mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12 in its ground state.
• Originally lightest, given value 1 and all other elements were measured relative to that. This meant it had no units.
• The unified atomic mass unit is u or Dalton (Da)
• Mass spectrometry is used to qualitatively and quantitatively identify elements present in a compound or mixture.
• The basic principle of mass spectrometry is that when charged particles move through a magnetic field they change direction, when the charge on particles is the same, the particles with the lower mass will experience a greater degree of deflection than heavier particles. When the mass is the same, particles with higher charge will experience a greater degree of deflection.
• The heavier the ion, the less it will be deflected within the magnetic field.
• ions of different charge can be produced in a mass spectrometer, the most common charge is +1.
• Isotopes are atoms of the same element with a different mass number or number of neutrons.
• Relative atomic mass and molar mass are derived from the average weight of an element.
• When calculating relative atomic mass each isotopic mass is multiplied by the percentage and divided by 100.
• Mass spectrometry is used to measure the mass of atoms or molecules. You can use it to determine the mass of each isotope, relative to the Carbon-12 standard. You can also use it to calculate the relative abundances of the isotopes in the sample.
• Data recorded from a mass spectrometer is presented graphically as a mass spectrum. It plots the relative abundance of each ion against its mass-to-charge ratio.
• To calculate relative atomic mass via the percentage abundance of isotopes you do: sum(% abundance of isotope times isotope mass) divided by 100.
• To calculate relative atomic mass via signal peaks you must first calculate the total peak height for all isotopes. % abundance = peak height divided by total peak height times 100. Once you've found the percentage abundances you can use the normal calculation.