Isotopes & Relative Atomic Mass
- Isotopes are different atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
- Isotopes can also be described as atoms of the same elements but with different mass numbers
- Therefore, the mass of an element is given as relative atomic mass (Ar) by using the average mass of the isotopes
- The relative atomic mass of an element can be calculated by using the relative abundance values by using the following equation:
- The relative abundance of an isotope is either given or can be read off the mass spectrum
Worked example
Calculating the relative atomic mass of oxygen
A sample of oxygen contains the following isotopes:
What is the relative atomic mass of oxygen in this sample, to 2 decimal places?
- 16.00
- 17.18
- 16.09
- 17.00
Answer
The correct answer option is A
-
- Ar =
- Ar = 16.0044
- Ar = 16.00