How to calculate atomic mass of isotopes?

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

The atomic weight of an element depends on the abundance of its isotopes.If you know the mass of the isotopes and the fractional abundance of the isotopes, you can calculate the element's atomic weight. read more

The first is the atomic mass, or the mass of one atom of each isotope. Isotopes with more neutrons have more mass. For example, the silver isotope Ag-107 has an atomic mass of 106.90509 amu (atomic mass units). The isotope Ag-109 is slightly heavier with a mass of 108.90470. read more

However, because atomic masses, when expressed in these terms, are incredibly small, atomic mass is often expressed in unified atomic mass units (usually shortened to "u" or "amu"). The standard for one atomic mass unit is equal to 1/12th of the mass of a standard carbon-12 isotope. read more