U

Uranium

IUPAC: Uranium

U Elements CAS 7440-61-1
Quick Reference
Formula / NotationU
CAS Number7440-61-1
Molecular Weight238.03
Melting Point1132.0
Boiling Point4131.0
Density19.1
AppearanceSilvery-grey lustrous metal, hard and malleable
Also Known AsU, uranium metal, natural uranium
CategoryElements

What is Uranium?

Uranium is a silvery-grey radioactive metal with atomic number 92, the heaviest naturally occurring element. It was discovered in 1789 by Martin Heinrich Klaproth. Uranium has three naturally occurring isotopes: U-238 (99.27%), U-235 (0.72%), and U-234 (0.006%). U-235 is fissile — it can sustain a nuclear chain reaction. The element is named after the planet Uranus.

Formula & Notation

U

IUPAC Name: Uranium

Other Names / Synonyms: U, uranium metal, natural uranium

Properties & Characteristics

Atomic number: 92. Atomic mass: 238.03 g/mol. Period 7, f-block (actinide series). Density: 19.1 g/cm³ (one of the densest metals). Melting point: 1132°C. Boiling point: 4131°C. Crystal structure: orthorhombic (α-phase at room temperature). Electronegativity: 1.38 (Pauling). Naturally occurring isotopes: U-238 (t½ = 4.47×10⁹ yr), U-235 (t½ = 7.04×10⁸ yr), U-234 (t½ = 2.46×10⁵ yr). All isotopes are radioactive — alpha emitters.

Physical Data

PropertyValue
Melting Point1132.0
Boiling Point4131.0
Density19.1
Molecular Weight238.03
AppearanceSilvery-grey lustrous metal, hard and malleable

Uses & Applications

Nuclear fuel: U-235 used in nuclear reactors (enriched to 3–5%) and weapons (enriched to >90%). Depleted uranium (mostly U-238): armor-piercing ammunition and radiation shielding. Historical: uranium glass (yellow/green fluorescent glass). Uranium compounds: used in photography, ceramics (orange-red glazes). Research: nuclear physics.

Safety Information

Radioactive — all isotopes emit alpha particles; some also emit beta and gamma radiation. Alpha emitter: dangerous if inhaled or ingested. Heavy metal toxicity: nephrotoxic (kidney damage). Depleted uranium: lower radioactivity but heavy metal toxicity concern. Natural uranium: regulated under nuclear material laws. Enriched uranium: strict security regulations. Pyrophoric as fine powder — fire risk. IAEA safeguards apply.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Uranium
Formula U
CAS Number 7440-61-1
Molecular Weight 238.03
Category Elements
Synonyms U, uranium metal, natural uranium

Frequently Asked Questions

Uranium is a silvery-grey radioactive metal with atomic number 92, the heaviest naturally occurring element. It was discovered in 1789 by Martin Heinrich Klaproth. Uranium has three naturally occurring isotopes: U-238 (99.27%), U-235 (0.72%), and U-234 (0.006%). U-235 is fissile — it can sustain a nuclear chain reaction. The element is named after the planet Uranus.

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