If a krypton atom has a mass of 84 and an iron atom has a mass of 56 and the distance between particles was the same, which atom is denser and why

Phosgene (carbonyl chloride), cocl2, is an extremely toxic gas that is used in manufacturing certain dyes and plastics. phosgene can be produced by reacting carbon monoxide and chlorine gas at high temperatures: co(g) cl2(g)⇌cocl2(g) carbon monoxide and chlorine gas are allowed to react in a sealed vessel at 477 ∘c . at equilibrium, the concentrations were measured and the following results obtained: gas partial pressure (atm) co 0.830 cl2 1.30 cocl2 0.220 what is the equilibrium constant, kp, of this reaction