How does atmospheric pressure at sea level compare to the atmospheric pressure on the top of a mountain? Explain.

At the top of a mountain the molecules are less dense and there is less air pressure. While at sea level the molecules are more dense and there is more air pressure.

gravity causes stares to cluster i think so

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)