The Keggin structure is made of twelve transition metal centers with this geometry along with a central heteroatom. For 10 points each:
[10e] Name this geometry that is displayed by the metal centers in the vast majority of polyoxometalates, since they are each bonded to six oxygen atoms and have no lone pairs.
ANSWER: octahedral [accept word forms]
[10h] This element forms huge wheel-shaped or spherical polyoxometalates that can have over a hundred metal centers. Salts of those anions are called this element’s namesake blue and are a sensitive test for reducing agents.
ANSWER: molybdenum [or Mo]
[10m] The most typical heteroatom for polyoxometalates, as in the Keggin-structure heteropolyacids made from molybdenum and tungsten, is derived from this tetrahedral oxyanion whose central atom has a 5+ oxidation state.
ANSWER: phosphate [or PO43-]
<Gerhardt Hinkle, Chemistry>