Explanation:
one mole contains Avogadro number of particles
So,
40g( the atomic mass) contains 6.023× 10^23 atoms.
so 1 g contains 40÷(6.023×10^23)
so, 52.3 g contains (40×52.3) ÷6.023×10^23
= 3.47× 10^-21
