The number of atoms in a given mass of a substance can be calculated using Avogadro's number, which is approximately 6.022 × 10^23 atoms/mol. However, in your example, you have mentioned the mass of helium (He) as 52 atomic mass units (amu).
Atomic mass units (amu) are a unit of mass used to express atomic and molecular weights. They represent a relative scale based on the mass of a carbon-12 atom. The atomic mass of helium is approximately 4 amu. Therefore, 52 amu of helium would correspond to 52/4 = 13 helium atoms.
So, in this case, the number of atoms is correctly calculated as 13, not 13 × (6.022 × 10^23) atoms. The value of Avogadro's number is the number of atoms or molecules per mole, and it is not directly related to the mass given in atomic mass units.