Which of the following has the greatest mass, in grams?

A mole of atoms is significantly bigger than a few atoms of any other element. Avogadro's number is huge.

In this case, 0,5 moles of Pb is heavier than 2.0 moles of chlorine. Look at the periodic table

in the beginning you are able to decrease fee the atom of silver and 25 atoms of lead. a million mole of Fe weighs fifty 5.847g so 0.3 moles weighs fifty 5.847 x 0.3 = sixteen.745g. a million mole of Hydrogen weighs a million.008g. So 0.3 mol Fe is the heaviest.

1/2 mole of lead atoms (atomic weight 205) would outweigh 2 moles of chlorine (atomic weight 35) by about 30% and would outweight one atom of gold or 25 atoms of mercury by about 10^21 %

the lead because of the avogadro's constant the atom ones are too small, from memory i think the molecular mass of chlorine is more than 4 times lighter than lead so it's lead.

25 atom of mecrury

gold, because it is the highest on the periodic table of elements, and it weighs a lot more than the rest