in 1 mole there are=6.02*10^23 particles so there are 2 cl atoms 1.81*10^24 MgCl2 should containt 2*(1.81*10^24) atoms...2*1.8*10^24 = 3.6 * 10^24 as we knw 1 mole contains 6.02*10^23 particle so x mole contains 3.6*10^24 particle so approximately there are 6 moles of chlorine atoms hope it helps
