In the image below, there are eight samples of different ELEMENTS. Each sample

is exactly 1 mol. Why are the masses of each sample different? The mass of 1
mole of each unique sample is different because the
of the
individual
are different.

The mass of each element is determined by its atomic mass, which is the sum of the number of protons and neutrons in the nucleus of the atom. Since each element has a different number of protons and neutrons, the mass of each element is different.