With the exception of helium and neon, which have large calculated electronega tivities and no known stable compounds, fluorine has the largest value, and electroneg ativity decreases toward the lower left corner of the periodic table. Hydrogen, although usually classified with Group 1 (IA), is quite dissimilar from the alkali metals in its electronegativity, as well as in many other properties, both chemical and physical. Hy drogen's chemistry is distinctive from all the groups.