Short answers, pulled from the story.
French chemist Eugène-Anatole Demarçay isolated europium in 1901 after suspecting samarium contamination in 1896. William Crookes first noted spectral anomalies in 1885, and the discovery was confirmed by Crookes in 1905.
A single centimeter of pure europium metal turns from gleaming silver to a dull dark brown crust within a few days of air exposure. The metal ignites spontaneously in air at temperatures between 150 and 180 degrees Celsius to form europium oxide.
Europium compounds serve as the primary source of red phosphors used in color television sets and fluorescent lamps. Each screen contains between 0.5 and 1 gram of europium oxide to create the white light found in helical fluorescent bulbs.
The largest known deposit of europium is found in the Bayan Obo iron ore deposit in Inner Mongolia. This deposit contains an estimated 36 million tonnes of rare-earth element oxides.
Studies show that europium chloride has an acute intraperitoneal LD50 toxicity of 550 mg/kg and an acute oral LD50 toxicity of 5000 mg/kg. The element has no significant biological role in the human body and is generally considered non-toxic when handled with standard precautions.