RE: # of moluclues in salt

On average, a grain of table salt (Sodium Chloride, NaCl) has a mass of about 100µg (one ten-thousandth of a gram). The number of molecules in a substance can be attained through Avogadro's number, 6.022 x 10²³ molecules per mole of compound. So, first we convert to moles: the molecular weight of salt is 58.44 grams per mole, so there are 1.71 x 10^-6 moles per grain. If we multiply this by Avogadro's number, we get 1.03 x 10¹⁸ molecules of NaCl per grain of table salt.

In American english, that's about one quintillion, or one billion billion, molecules in a single grain of salt.