heptavalent

from The Collaborative International Dictionary of English v.0.48

Heptavalent \Hep*tav"a*lent\, a. [Hepta- + L. valens, p. pr. See
   {Valence}.] (Chem.)
   Having seven units of attractive force or affinity; -- said
   of heptad elements or radicals.
   [1913 Webster]