How many moles are 1.20 x10^25 atoms of phosphorus?

1 mole of any substance contain Avogadro's number of molecules so we can calculate the number of moles by dividing the provided number of atoms over Avogadro's number to obtain the number of moles 

Answer : 19.9 moles of phosphorus

  Solution : Atoms / Avogadro's number (6.022 x 10²³ atoms/mol)

 1.20 x 10²⁵ atoms / 6.022 x 10²³ = 19.927

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.