2.2 Atoms, ions and compounds

• What is the formula for a silver ion?

  Ag+
• What is the formula for a zinc ion?

  Zn2+
• What is the formula for an ammonium ion?

  NH4+
• What is the formula for a hydroxide ion?

  OH-
• What is the formula for a sulphate ion?

  SO4^2-
• What is the formula for a carbonate ion?

  CO3^2-
• What is the formula for a nitrate ion?

  NO3-
• What is the definition of relative atomic mass?

  Weighted mean mass of the atoms of an element when compared to a 1/12 of the mass of an atom of carbon-12
• What is the definition of relative isotopic mass?

  Mass of an atom of an isotope when compared to a 1/12 of the mass of carbon-12
• What is the formula to calculate relative atomic mass?

  (% abundance x mass) + (% abundance x mass) / 100
• How does a mass spectrometer work?

  Ionisation:

  Electron knocks off an electron from the substance giving it a positive charge

  Acceleration:

  The negative plate attracts positive ion

  Deflection:

  Uses a magnetic field. The higher the mass of the sample, the stronger the magnetic field needs to be so it reaches the detector

  Detection:

  Creates an impulse which creates a peak
• What are the uses of a mass spectrometer?

  • Monitoring the breath of patients during surgery whilst under anaesthetic

  • Detecting banned substances such as steroids in athletics

  • Analysing molecules in space

  • Detecting traces of toxic chemicals in marine life
• What do the key features of a mass spectra show?

  Number of peaks - number of isotopes

  Height of the peaks - abundance