Short answers, pulled from the story.
Yttrium is a silvery-metallic transition metal with atomic symbol Y and atomic number 39. It is chemically similar to the lanthanides and is classified as a rare-earth element. It is never found in nature as a free element, always occurring alongside lanthanide elements in rare-earth minerals.
Yttrium is named after ytterbite, the mineral first identified in 1787 by Carl Axel Arrhenius. Arrhenius named the mineral after the Swedish village of Ytterby, where he found the original rock sample in an old quarry. When a previously unidentified element was later found within the mineral, it took the name yttrium from the mineral.
Yttrium was widely used as a host lattice in the red phosphors of color television cathode ray tube displays. Yttrium oxide or yttrium oxysulfide absorbed energy from the electron gun and transferred it to europium phosphors, which emitted the red color. Today cerium-doped yttrium aluminium garnet (YAG:Ce) serves as a key phosphor in white LEDs.
Yttrium-90, a radioisotope with a half-life of 64 hours, is used to label drugs including edotreotide and ibritumomab tiuxetan for treating cancers such as lymphoma, leukemia, and liver, ovarian, colorectal, pancreatic, and bone cancers. It adheres to monoclonal antibodies that bind to cancer cells and destroy them through intense beta radiation. Millions of yttrium-90 microspheres are also used in radioembolization to treat hepatocellular carcinoma and liver metastasis.
Yttrium barium copper oxide (YBCO), developed at the University of Alabama in Huntsville and the University of Houston in 1987, was only the second material known to achieve high-temperature superconductivity and the first to operate above 77.1 K, the boiling point of liquid nitrogen. Because liquid nitrogen is far less expensive than the liquid helium needed by conventional superconductors, YBCO opened the door to more economically viable applications.
YInMn blue is an intensely blue, non-toxic, inert, and fade-resistant pigment made by combining yttrium, indium, and manganese. Professor Mas Subramanian and colleagues at Oregon State University discovered it in 2009. It was the first new blue pigment discovered in two hundred years.