A1 - Atomic Structure And Isotopes

Question 1

What is relative isotopic mass?

Answer 1

The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Question 2

What is relative atomic mass?

Answer 2

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.

Question 3

What is an isotope?

Answer 3

Atoms with the same number of protons but different number of neutrons.

Question 4

Briefly, how do you determine relative atomic mass?

Answer 4

• Using a mass spectrometer
  1. Sample is placed in the mass spectrometer
  2. The sample is vaporised then ionised to form positive ions
  3. The ions are accelerated. Heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each isotope are separated
  4. The ions are detected on a mass spectrum as a mass-to-charge ratio m/z.

Question 5

How do you determine relative isotopic mass?

Answer 5

• The mass spectrometer can also record the accurate m/z ratio for each isotope so that accurate values of relative isotopic mass can be measured