<p><strong>Noun:</strong></p><ul><li>A grayish-white, lustrous, somewhat ductile and malleable, radioactive metallic element present in monazite.</li><li>Used as a source of nuclear energy, as a coating on sun-lamp and vacuum-tube filament coatings, and in alloys.</li><li>Symbol: Th</li><li>Atomic number: 90</li><li>Atomic weight: 232.038</li><li>Density: 11.7</li></ul>