The Element Uranium [Click for Isotope Data] Atomic Number: 92
Atomic Weight: 238.02891 Melting Point: 1408 K (1135°C or
2075°F) Boiling Point: 4404 K (4131°C or 7468°F) Density: 18.95
grams per cubic centimeter Phase at Room Temperature: Solid
Element Classification: Metal Period Number: 7 Group Number:
none Group Name: Actinide What's in a name? Named for the planet
Uranus. Say what? Uranium is pronounced as you-RAY-nee-em.
History and Uses: Uranium was discovered by Martin Heinrich
Klaproth, a German chemist, in the mineral pitchblende
(primarily a mix of uranium oxides) in 1789. Although Klaproth,
as well as the rest of the scientific community, believed that
the substance he extracted from pitchblende was pure uranium, it
was actually uranium dioxide (UO2). After noticing that 'pure'
uranium reacted oddly with uranium tetrachloride (UCl4), Eugène-
Melchoir Péligot, a French chemist isolated pure uranium by
heating uranium dioxide with potassium in a platinum crucible.
Radioactivity was first discovered in