atomic structure

• explain the term relative atomic mass.

  the average mass of an atom compared to 1/12 th of a carbon-12 atom.
• describe how the molecules are ionised using electrospray ionisation.


  molecule is dissolved in a volatile solvent and then injected through a needle. The molecule then gains a H+
• explain how ions are detected and relative abundance is measured in a TOF mass spectrometer.


  Ions are accelerated towards a negative plate and gain an electron when it hits the plate. The relative abundance is proportional to the size of the current.
• state why the isotopes have the same chemical properties.


  same electron configuration.
• give two reasons why it is necessary to ionise the isotopes of chromium before they can be analysed in a TOF mass spectrometer.

  ions are accelerated towards a negative plate and create a current once they hit the detector.
•  state how the relative abundance of isotope is determined in a TOF mass spectrometer.

  isotope accelerates towards the negative plate and gains an electron, relative abundance depends on the size of the current.
• Give an equation to represent the ionisation of P in the process of electrospray ionisation.


  P + H+ → PH+