What is the mass of 1 mol of an element?
It is the molar mass of the element.
The molar mass of an element is its atomic weight (relative atomic mass) on the periodic table in grams/mole, or g/mol.
For example, the atomic weight of oxygen (O) on the periodic table is
It is the atomic weight in grams for the metric system.
The "mass" of an element is based on a comparison to an accepted standard mass, and may also be subject to the averaging of variations in normal isotopes of an element.
The "mol" is simply a number of units as derived by Avogadro to be