50 free Uranium trivia questions with answers — science & nature quiz, new questions added Aug 2026.
This uranium trivia quiz covers the heaviest element found in nature in any quantity, and the one that made the nuclear age. The easy questions handle the basics: its symbol and atomic number, the planet it was named after, why it is radioactive, and which isotope powers reactors and bombs. The harder end goes into the science and the history: Klaproth's yellow precipitate in 1789, Becquerel's fogged photographic plate, Hahn and Strassmann finding barium in 1938, Meitner and Frisch naming fission, Chicago Pile-1, Little Boy over Hiroshima, the natural reactors that ran at Oklo 1.7 billion years ago, uranium glass and Fiestaware, yellowcake, gas centrifuges, depleted uranium armour, and which countries dig up most of it today. Every answer was checked against the element's encyclopaedia entry before publishing and the supporting sentence is stored with each question. Our periodic table, chemistry and nuclear-themed quizzes are the natural next stop.
30 of 50 questions with answers and explanations. Play the quiz
Q 01What is uranium's atomic number?
92
Its symbol is U and it sits in the actinide series; it is the highest-numbered element found naturally in significant amounts.
Q 02Uranium was named after which planet?
Uranus
William Herschel had discovered the planet only eight years before the element was found in 1789.
Q 03Which German chemist is credited with discovering uranium in 1789?
Martin Heinrich Klaproth
He precipitated a yellow compound from the ore and thought the black powder he then made was the metal; it was actually an oxide.
Q 04In which mineral was uranium first discovered?
Pitchblende
Pitchblende is uraninite, uranium's natural oxide, and remains the most common uranium ore.
Q 05Who first isolated uranium metal, in 1841, by heating uranium tetrachloride with potassium?
Eugène-Melchior Péligot
He was professor of analytical chemistry at the Conservatoire National des Arts et Métiers in Paris.
Q 06Who discovered radioactivity in 1896 using a uranium salt left on a photographic plate?
Henri Becquerel
He found the plate in a drawer had become 'fogged' by invisible rays from the potassium uranyl sulfate.
Q 07Which isotope makes up over 99% of natural uranium?
U-238
It has 146 neutrons; the fissile isotope has only 143.
Q 08Which uranium isotope is fissile and used in reactors and weapons?
U-235
It is only about 0.7% of natural uranium, which is why fuel and bombs need enrichment.
Q 09What is the half-life of uranium-238?
About 4.5 billion years
That makes it ideal for dating the oldest igneous rocks through uranium-lead dating.
Q 10Uranium's density is about 70% higher than that of which metal?
Lead
At 19.1 g/cm3 it is only slightly less dense than gold and tungsten.
Q 11Which two scientists found barium among the products of bombarding uranium with neutrons in 1938?
Otto Hahn and Fritz Strassmann
The work was done in Hahn's Berlin laboratory; the theoretical interpretation came a year later.
Q 12Who published the physical explanation of uranium splitting in February 1939 and named it 'nuclear fission'?
Lise Meitner and Otto Robert Frisch
Frisch was Meitner's nephew; she had fled Nazi Germany the previous year.
Q 13On average, how many neutrons are released by each fission of uranium-235?
About 2.5
Q 21The world's first commercial-scale nuclear power station began generating in June 1954. Where?
Obninsk, Soviet Union
Calder Hall followed in 1956 and Shippingport in 1958; the submarine USS Nautilus went nuclear in 1954 too.
Q 22Natural nuclear reactors that ran 1.7 billion years ago were discovered in 1972 at which mine?
Oklo, in Gabon
Back then uranium-235 made up about 3% of uranium, enough for a chain reaction with groundwater as moderator.
Q 23Commercial nuclear power plants typically use fuel enriched to roughly what level of uranium-235?
About 3%
Enough of them hitting other nuclei is what sustains a chain reaction, confirmed in 1939.
Q 14Fermi's team at first mistook uranium fission products for new elements 93 and 94. What were they named?
Ausenium and hesperium
Orso Mario Corbino, dean at Rome's Sapienza University, coined the names; the real elements 93 and 94 were identified a few years later.
Q 15Who separated the world's first sample of uranium-235, on 29 February 1940?
Alfred O. C. Nier
He used an instrument he built himself at the University of Minnesota; John Dunning confirmed its fissility with Columbia's cyclotron the next day.
Q 16Where was Chicago Pile-1, the first self-sustaining artificial chain reaction, built in 1942?
Under the stands of Stagg Field
Fermi's team stacked 360 tonnes of graphite, 53 tonnes of uranium oxide and 5.5 tonnes of uranium metal.
Q 17Which nuclear weapon, dropped on Hiroshima, relied on uranium fission?
Little Boy
The Trinity test device and Fat Man, dropped on Nagasaki, used a different fissile element.
Q 18What is the smallest amount of uranium-235 said to be enough for an atomic bomb?
About 15 lb (6.8 kg)
The Hiroshima bomb exploded with the force of about 12,500 tonnes of TNT.
Q 19What was the name of Germany's wartime nuclear research project?
The Uranverein
The 'uranium club' was hampered by infighting, exiled scientists and a mistake about impurities in graphite that ruled it out as a moderator.
Q 20Which installation first generated nuclear electricity, lighting four bulbs on 20 December 1951?
Experimental Breeder Reactor I in Idaho
The nearby town of Arco later became the first anywhere to run entirely on nuclear electricity, from BORAX-III.
Only the CANDU and Magnox designs can run on unenriched uranium; US Navy reactors use highly enriched fuel.
Q 24One kilogram of uranium-235, fully fissioned, releases as much energy as roughly how much coal?
About 1,500 tonnes
That is about 20 terajoules from a single kilogram.
Q 25What was the cheapest and leading method of enriching uranium in the 2020s?
Gas centrifuges
They exploit the tiny mass difference between the isotopes; gaseous diffusion was the Manhattan Project's method.
Q 26Which white, easily sublimed compound of the metal is used in enrichment because its vapour behaves like a gas?
Uranium hexafluoride (UF6)
UF6 is the most volatile uranium compound known.
Q 27What is 'yellowcake'?
A uranium oxide concentrate from milled ore
It contains at least 75% U3O8 and is calcined before refining and conversion.
Q 28Which country mined 39% of the world's uranium in 2024?
Kazakhstan
It has dominated the market since 2010; Canada and Namibia came next in 2024.
Q 29Which country holds 28% of known uranium reserves and the largest deposit, at Olympic Dam?
Australia
There is also a significant reserve at Bakouma in the Central African Republic.
Q 30High-grade ores in which Canadian basin can average up to 23% uranium oxides?
Athabasca
Typical low-grade ore holds only 0.01 to 0.25%.