 The reason is that with inorganic lead compounds elements such as nitrogen, oxygen and the halides have a much higher electronegativity than lead itself and the partial positive charge on lead then leads to a stronger contraction of the 6s orbital than the 6p orbital making the 6s orbital inert; this is called the inert pair effect.By far the most important organolead compound is tetraethyllead, formerly used as an antiknock agent in gasoline intended for internal combustion engines.The most important lead reagents for introducing lead are lead tetraacetate and lead chloride.