mass spectrometer and atomic mass

10/2/25

purpose of mass spectrometer

• a sample is heated, vapourized and ionized

• travels down to the detector

• calculated force of the magnets that bend the sample

• based on the magnetic force you know the masses and you know the relative amount of the

isotope

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element

how to determine average atomic mass?

• Calculate average of the mass of the isotopes

• Multiply masses by percentage

• add them up

Determine the average atomic mass of a sample of magnesium based on the percent composition data in the picture

MAvg = (CMg-24 x MMg-24) + (CMg-25 x MMg-25) + (CMg-26 x MMg-26)

= (0.7890)(23.98504 amu) + (0.1000)(24.985839 amu) + (0.1110)(25.982595 amu)

= 24.306852 amu

= 24.31 amu