This element "borrows" an electron from the 4s orbital to completely fill its 3d orbital, making it paramagnetic.
A highly effective catalyst for many C-C and C-X bond-forming reactions is this element complexed with a bis(oxalozine) ligand. 1,4-disubstituted 1,2,3-triazoles can be created by an azide-alkyne cycloaddition catalyzed by this element in a seminal reaction of click chemistry developed in the labs of Fokin and Sharpless. Diazonium salts are treated with the chloride of this element to create aryl halides in the Sandmeyer reaction. In hemocyanin, this element binds reversibly to oxygen molecules. This element "borrows" an electron from the 4s orbital to completely fill its 3d orbital, making it paramagnetic. This element's citrate or tartrate is used to test for reducing sugars and aldehydes in Benedict's and Fehling's test, respectively. This element is found with lithium in Gilman's reagent. For 10 points, name this element with symbol Cu.
A highly effective catalyst for many C-C and C-X bond-forming reactions is this element complexed with a bis(oxalozine) ligand.
copper [or Cu before it is read]