Question: how many atoms are there in a grain of salt?
Answer: Now it is a simple matter to find how many atoms there are in a grain of salt. (Note that one mole contains Avogadro's number of atoms, which is 6.02x1023.) So a grain of salt contains about: 5.85x10-5 gr/ (29.25 gr / 6.02x1023) = 1.2x1018 atoms, half of which are sodium atoms.