How do you find the atomic mass of an element?

To calculate the atomic mass of a single atom of an element, add up the mass of protons and neutrons. Example: Find the atomic mass of an isotope of carbon that has 7 neutrons. You can see from the periodic table that carbon has an atomic number of 6, which is its number of protons. read more

There is no need to 'calculate' it, you can find the atomic molar mass of an element by looking at it's atomic mass on the periodic table. However, if an element is diatomic (like "Br"_2), you'll have to double its molar mass. read more

Three Methods: Finding Atomic Mass Readings on the Periodic Table Calculating Atomic Mass for an Individual Atom Calculating Relative Atomic Mass (Atomic Weight) for an Element Community Q&A Atomic mass is the sum of all the protons, neutrons, and electrons in a single atom or molecule. read more

If you know the mass of the isotopes and the fractional abundance of the isotopes, you can calculate the element's atomic weight. The atomic weight is calculated by adding the mass of each isotope multiplied by its fractional abundance. read more