Why does Uranium have the symbol U?

The symbol U is simply derived from the first letter of the element name "uranium," which itself was named after the planet Uranus. Martin Heinrich Klaproth isolated uranium oxide in 1789, shortly after Uranus was discovered in 1781, and named the new element in its honor.

Is Uranium dangerously radioactive?

Natural uranium is only mildly radioactive — far less so than many other radioactive materials. Its long half-lives (U-238: 4.47 billion years; U-235: 703 million years) mean it decays very slowly. The primary health risk from metallic uranium is chemical toxicity to the kidneys rather than radiation exposure, under normal handling conditions with appropriate precautions.

What is enriched uranium?

Natural uranium contains about 0.72% U-235 (the fissile isotope) and 99.27% U-238. Enriched uranium has an increased proportion of U-235. Low-enriched uranium (LEU, 3–5% U-235) is used in commercial reactor fuel. Highly enriched uranium (HEU, ≥20% U-235) is used in research reactors and nuclear weapons.

What is depleted uranium?

Depleted uranium (DU) is the byproduct of uranium enrichment — it contains less U-235 (~0.2–0.3%) than natural uranium. DU is extremely dense (19.1 g/cm³) and is used in radiation shielding, aircraft counterweights, armor-piercing projectiles, and as a balancing material in aircraft control surfaces.

How many naturally occurring isotopes does Uranium have?

Uranium has three naturally occurring isotopes: U-238 (99.274% abundance), U-235 (0.720%), and U-234 (0.0054%). All are radioactive. U-238 and U-235 are the parents of two major radioactive decay chains. U-234 is produced by the alpha decay of U-238 and is in secular equilibrium with it.

Why is U-235 used in nuclear reactors and weapons?

U-235 is fissile — it can sustain a chain reaction when struck by slow (thermal) neutrons. When a U-235 nucleus absorbs a neutron it typically splits into two smaller nuclei, releasing 2–3 neutrons and roughly 200 MeV of energy. This energy release is about 50 million times greater per atom than burning carbon, making it an extraordinarily concentrated energy source.

Uranium Element Properties

Look up every key property of Uranium (U, Z=92) — from atomic mass and electron configuration to melting point, radioactivity, and nuclear applications.

U 92

Uranium (Uranium)

Atomic number 92 · Group 3 (f-block) · Period 7 · Actinide

A dense, silvery-gray radioactive metal — the heaviest naturally occurring element and the cornerstone of nuclear energy and weapons technology.

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Identity & Classification

Atomic Structure

Physical Properties

Thermodynamic Properties

Chemical Properties

Notable Isotopes

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Summary

Uranium (symbol U, atomic number 92) is a dense, silvery-gray radioactive actinide metal and the heaviest naturally occurring element. It sits at the bottom of the periodic table in the f-block and is weakly radioactive — all isotopes are unstable. Uranium is best known as the primary fuel for nuclear reactors and atomic weapons, but it also has civilian uses in radiation shielding, counterweights, and as a coloring agent in glass. This reference card consolidates its atomic, physical, chemical, thermodynamic, and nuclear properties in one searchable view.

How it works

The page loads a curated dataset of Uranium properties organized by category.
Properties are grouped into thematic sections: identity, atomic structure, physical, thermodynamic, chemical, and isotopes.
Use the search box to filter any property by name or value.
Click any value to copy it to the clipboard instantly.
Isotope data covers naturally occurring and key artificial isotopes with half-lives.

Use cases

Quick reference during nuclear chemistry or physics coursework.
Verify data for lab reports and research papers on actinides.
Study periodic trends at the high end of the actinide series.
Engineering calculations for uranium fuel enrichment and reactor design.
Compare uranium isotopes for nuclear fuel cycle analysis.
Teaching radioactive decay, fission, and nuclear properties.
Research on depleted uranium for shielding and ballistic applications.
Environmental and radiological safety assessments involving uranium.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu