Short answers, pulled from the story.
Jean Charles de Marignac observed distinct spectroscopic lines in 1880, but Paul-Émile Lecoq de Boisbaudran officially named the element gadolinium in 1886. Johan Gadolin first analyzed the specific ore from Ytterby near Finland in 1794.
Gadolinium possesses 64 electrons arranged in the configuration [Xe]4f75d16s2. At room temperature the metal crystallizes into a hexagonal close-packed alpha-form structure, while temperatures above 293 kelvins transform it into a body-centered cubic beta-form.
Mining operations extract crushed minerals using hydrochloric acid or sulfuric acid to convert insoluble oxides into soluble chlorides or sulfates. Pure metal finally emerges by heating the oxide with calcium at 1200 degrees Celsius within an argon atmosphere after ion exchange chromatography separates rare-earth ions.
Solutions of organic gadolinium complexes serve as intravenous contrast agents because paramagnetic ions increase nuclear spin relaxation rates to enhance image clarity. About a dozen different Gd-chelated agents have received approval worldwide for clinical use, and toxicity decreases by a factor of thirty-one when chelation occurs.
Gadolinium-157 holds the highest thermal-neutron capture cross-section among any stable nuclide at approximately 259,000 barns. Some CANDU reactor types utilize gadolinium as a secondary emergency shut-down measure while nuclear marine propulsion systems employ the element as a burnable poison to control reactions.
As little as one percent of gadolinium improves workability of iron and chromium alloys significantly while Gadolinium barium copper oxide set a world record in 2014 trapping 17.6 teslas within bulk superconductors. Solid oxide fuel cells utilize gadolinium-doped ceria to achieve high ionic conductivity at lower operating temperatures.