To determine the molar mass of an element, what must be known?

To determine the molar mass of an element, it is essential to know the average atomic mass. The average atomic mass is calculated based on the weighted average of the masses of all the isotopes of that element, accounting for their relative abundances. This value reflects how much one mole of the element weighs in grams and is directly used to express the molar mass in the periodic table.

The average atomic mass provides a more accurate depiction of what one mole of the element consists of in terms of weight, as isolated isotopes may have different masses, and their natural occurrence must be considered. By using the average atomic mass, one can precisely relate it to the number of moles when performing stoichiometric calculations in analytical chemistry, thus making it crucial for this measurement.