Uranium Trivia
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48 free Uranium trivia questions with answers — science & nature quiz, new questions added Oct 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 48 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 02Which astronomer discovered Uranus, the planet uranium is named after?
Herschel
Herschel. William Herschel spotted it from his garden in Bath in 1781 and tried to name it George's Star after King George III, but the name did not stick.
Q 03Which chemist is credited with discovering uranium in 1789?
Martin Heinrich Klaproth
Martin Heinrich Klaproth. The Berlin chemist believed the black powder he had made was the new metal itself; it was only an oxide, and pure uranium was not isolated for another half-century.
Q 04In which mineral was uranium first discovered?
Pitchblende
Pitchblende. The heavy black ore turned out to be more radioactive than the uranium in it could explain, and chasing that puzzle led to the discovery of two more new elements.
Q 05Whose signed letter of 1939 warned President Roosevelt that uranium could be turned into extremely powerful bombs?
Albert Einstein
Albert Einstein. The warning was really Leo Szilard's idea: he drafted it and had himself driven out to Einstein's Long Island holiday cottage for the one signature a president could not ignore.
Q 06Who discovered radioactivity in 1896 using a uranium salt left on a photographic plate?
Henri Becquerel
Henri Becquerel. He was testing whether light made uranium salts give off rays, but a plate shut away in a dark drawer fogged all the same, so the rays had to come from the uranium itself.
Q 07Who coined the word 'radioactivity' while studying the rays given off by uranium?
Marie Curie
Marie Curie. She took uranium's puzzling rays as the subject of her doctorate, found that thorium gave them off too, and needed a name for a property that clearly was not unique to one element.
Q 08Which uranium isotope is fissile and used in reactors and weapons?
U-235
U-235. Nobody could be sure which isotope did the splitting until 1940, when a Minnesota physicist separated a speck of it in a machine he had built himself and tests proved it was the one.
Q 09What is the half-life of uranium-238?
About 4.5 billion years
About 4.5 billion years. That is close to the age of the Earth itself, so roughly half the uranium-238 the planet started with is still here, which lets geologists date the very oldest rocks.
Q 10Uranium's density is about 70% higher than that of which metal?
Lead
Lead. Uranium is nearly as dense as gold, which is why the depleted metal makes a radiation shield that does the job in less space than lead itself.
Q 11Which two scientists found barium among the products of bombarding uranium with neutrons in 1938?
Otto Hahn and Fritz Strassmann
Otto Hahn and Fritz Strassmann. As chemists they hesitated to announce something physics said was impossible, since barium is barely half the weight of uranium, and wrote to an exiled colleague for help.
Q 12Who published the physical explanation of uranium's splitting in February 1939, naming it 'nuclear fission'?
Lise Meitner and Otto Robert Frisch
Lise Meitner and Otto Robert Frisch. Aunt and nephew worked it out in Sweden, where she had fled from Nazi Germany, yet the Nobel Prize for fission went to her old Berlin partner alone.
Q 13Which physicist led the team that achieved the first self-sustaining nuclear chain reaction, in Chicago in 1942?
Q 21Which country, beating Britain and America, opened the first nuclear power station to feed a public grid, in 1954?
Soviet Union
Soviet Union. Its small Obninsk plant, southwest of Moscow, fed five megawatts to the grid, and its graphite-and-water design became the prototype for the reactors later built at Chernobyl.
Q 22What did French scientists discover in 1972 in the uranium ore at Oklo, in Gabon?
Ancient natural reactors
Ancient natural reactors. Some two billion years ago the ore was rich enough in uranium-235 for groundwater to set off chain reactions that flickered on and off for a few hundred thousand years.
Q 23Commercial nuclear power plants typically use fuel enriched to roughly what level of uranium-235?
Enrico Fermi
Enrico Fermi. The news was phoned through in code as 'the Italian navigator has just landed in the New World'; he had left Mussolini's Italy only four years before.
Q 14Which secret wartime city was built to enrich uranium for the Manhattan Project?
Oak Ridge
Oak Ridge. The secret city in the Tennessee hills soon outgrew its planners' estimates and held about 75,000 people by 1945.
Q 15What kind of vessel became the first to put to sea under nuclear power, in 1955?
A submarine
A submarine. USS Nautilus signalled 'Underway on nuclear power' as she left harbour, and a reactor that needs no air let her stay submerged at speed for long stretches.
Q 16Chicago Pile-1, the first man-made nuclear reactor, was built in 1942 beneath what?
A football stadium's stands
A football stadium's stands. The team stacked their graphite and uranium in a rackets court under the University of Chicago's Stagg Field, with no radiation shielding at all.
Q 17Which nuclear weapon, dropped on Hiroshima, relied on uranium fission?
Little Boy
Little Boy. It worked by firing one piece of uranium down a gun barrel into another, a design so wasteful that less than 2% of its uranium actually fissioned.
Q 18What term describes the smallest amount of uranium-235 that can sustain a chain reaction?
Critical mass
Critical mass. In any smaller lump too many neutrons escape for the reaction to keep going, which is why the Hiroshima bomb held its uranium in two separate pieces until the last instant.
Q 19Which Nobel-winning physicist was the scientific head of Nazi Germany's 'Uranium Club' nuclear project?
Werner Heisenberg
Werner Heisenberg. His team never got a chain reaction going, partly because a faulty measurement on impure samples convinced the Germans that graphite would not work in a reactor.
Q 20In 1951 the first electricity ever generated by a nuclear reactor was just enough to power what?
Four light bulbs
Four light bulbs. Idaho's Experimental Breeder Reactor I lit them on 20 December 1951 and was soon powering its whole building; four years later a sister reactor lit the nearby town of Arco.
About 4%
About 4%. Natural uranium holds under 1% of the fissile isotope, so most reactors need only a modest boost, a world away from the 90% or so that a bomb requires.
Q 24What was the cheapest and leading method of enriching uranium in the 2020s?
Gas centrifuges
Gas centrifuges. Spinning the gas at enormous speed does the job on roughly a fiftieth of the electricity the old diffusion plants swallowed, which is why every enrichment plant now running uses them.
Q 25Which uranium compound is turned into a gas so that enrichment plants can work on it?
Uranium hexafluoride
Uranium hexafluoride. Known in the trade as 'hex', it is shipped as a white solid and turns to gas at only about 56 degrees C, which is what makes handling uranium as a gas practical.
Q 26What is 'yellowcake'?
A uranium oxide concentrate from milled ore
A uranium oxide concentrate from milled ore. Despite the name, what mills ship today is usually khaki, brown or black; only the concentrates of early mining days were truly yellow.
Q 27Which country mined 39% of the world's uranium in 2024?
Kazakhstan
Kazakhstan. It has led the world since overtaking Canada in 2009, yet it has had no working nuclear power plant of its own since 1999 and only voted to build one in 2024.
Q 28As of 2025, which country held more than a quarter of the world's known uranium resources, the largest share?
Australia
Australia. Much of it lies in one giant orebody, Olympic Dam, where uranium is a by-product of copper mining, yet Australia has no nuclear power plants and exports every tonne.
Q 29High-grade ores in which Canadian basin can average up to 23% uranium oxides?
Athabasca
Athabasca. Its ore runs about a hundred times richer than the world average, and the biggest mines there freeze the soft ground solid and cut the ore out by remote control.
Q 30In 2024, which mining method produced more than half of the world's uranium?
In-situ leaching
In-situ leaching. A solution pumped down wells dissolves the uranium where it lies and is pumped back up, so there is no pit, no waste rock and far less to build, which keeps it cheap.