This page covers the following topics:
2. Relative atomic mass
Isotopes are atoms of the same element, which have the same number of protons but a different number of neutrons. They are present in different levels of abundance. Some isotopes are radioactive.
Many isotopes are denoted by using the chemical symbol of an element and two additional numbers. The top number in such notation is the mass of an isotope in atomic units and the lower number is the charge of the nucleus, which matches the atomic number of an element.
Relative atomic mass is a weighted average mass of all the isotopes of an element. Weighted means that it takes into account the natural abundance of each isotope.
To find the relative atomic mass from given atomic masses of isotopes and their abundances, multiply corresponding atomic masses and their abundances in decimals and add the multiplication products together. If you use abundances as percentages, divide your final result by 100%.
What is the heaviest hydrogen isotope?
Magnesium has three stable isotopes, ²⁴Mg (79%), ²⁵Mg (10%) and ²⁶Mg (11%). What is the relative atomic mass of magnesium?
How many neutrons does ³⁷₁₇Cl have?
Chlorine has two stable isotopes, ³⁵Cl (75%) and ³⁷Cl (25%). What is the relative atomic mass of chlorine?
Copper has two main isotopes, ⁶³Cu and ⁶⁵Cu with their abundances respectively being 70% and 30%. What is the relative atomic mass of copper? The data provided has been adjusted for the question.
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