Why Are (MgO)n Clusters and Crystalline MgO So Reactive?

The electronic structures and chemical reactivities (toward H, Li, Li 2, and H 2 ) are examined for small (MgO) n clusters. It is postulated that decreases in the clusters' reactivity toward the above prototypical species as the cluster size ( n ) increases is related to the decrease in valence unsaturation that accompanies increases in n . Further, it is suggested that the known high reactivity of MgO powder and crystal is likely related to surface or defect sites that possess high levels of valence unsaturation.