High values of this quantity characterize a category of incompatible elements called HFSEs. The dependence of solubility on this quantity explains the cerium and europium anomalies. It’s not concentration, but this quantity is lower for elements in rocks formed from a tholeiitic magma than a calc-alkaline magma. Whether an element with variable values for this quantity partitions into mineral or melt is constrained by the dependence of this quantity on oxygen fugacity. Distinct values of this quantity are held by the iron atoms in magnetite. (10[1])Since this (10[1])quantity of the most stable species of calcium and strontium are the same, they substitute each other in minerals. Ferric (10[1])and ferrous iron differ in, for 10 points, what quantity, the number of electrons added or removed from an element? ■END■ (10[1]0[1])