Well none since molecules are a group of two or more atoms electrically bonded with one another. However, there are gases that does not naturally bond due to their stability and can be found in nature as pure elements. But these are not considered as molecules.
(By the way, these gases are the noble gases that can be found on the last column of the periodic table)
Although 1013.25 mb (760 mm Hg) is considered to be the standard atmospheric pressure at sea level, it does not mean that the pressure at this level has this value, actually this being 1011 mb.