Naming compounds I2O7?

The formula name is diIODINE heptOXide (diiodine heptoxide), I2O7. Where "di" [prefix in diIODINE] means the 2 atoms of Iodine. And, "hept" [prefix from hepta = 7] in heptOXide means the 7 atoms of Oxygen; the "ox" in heptOXide means the 1st two letters of the stem name for the 2nd element and + “ide.” The proper rule for naming covalent compounds: prefix + (name of 1st element) then, prefix + (stem name of 2nd element) + ide, where the prefixes are mono=1, di=2, tri=3, tetra=4, penta=5, hexa=6, hepta=7, octa=8, nona=9, and deca=10. Hope it helps.