The relative atomic mass of an element is determined by considering the isotopic composition of that element and the masses of its isotopes. Here's the general process for calculating the relative atomic mass:
Identify the isotopes: Determine the isotopes of the element and their respective abundances. Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei, resulting in different masses.
Determine the mass of each isotope: Find the atomic mass of each isotope by referring to experimental data or the periodic table. The atomic mass is usually given as a decimal number, and it represents the average mass of all naturally occurring isotopes of that element.
Calculate the weighted average: Multiply the mass of each isotope by its relative abundance (expressed as a decimal or a percentage) and then sum up these values. This calculation accounts for the different proportions of each isotope in a naturally occurring sample of the element.
Round off if necessary: Round the calculated value to the appropriate number of decimal places, usually according to the precision of the atomic mass given in the periodic table.
The resulting value is the relative atomic mass of the element, which represents the average mass of the atoms in a typical sample of that element. It is expressed in atomic mass units (amu) or grams per mole (g/mol).