Radon
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40 free Radon trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Radon is a gas you cannot see, smell or taste, yet it seeps out of the ground almost everywhere on Earth. It is radioactive, it is astonishingly rare, and it has one of the strangest histories of any element: feared by miners for centuries before anyone knew it existed, then bottled, bathed in and sold as a cure. These fun facts about radon are written as quiz questions. They cover where the gas comes from and why it collects in buildings, who discovered it and the names it went by before "radon" stuck, where it sits in the periodic table, and how homes are tested and fixed. Other questions follow radon to health resorts, into early cancer medicine, out into space and down into the mines. The quiz suits curious readers, chemistry students, homeowners puzzling over a radon test result, and anyone building a science round for trivia night. Every answer comes with a short explanation, and the difficulty runs from easy openers to a few questions for real enthusiasts.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Stanley Watras exposed America's radon problem in 1984 by tripping alarms at what kind of workplace?
A nuclear power plant
A nuclear power plant in Pennsylvania found him contaminated before its reactor had ever been fuelled. The radiation was traced to radon seeping into his own family home.
Q 02Radon gas tends to build up to its highest levels in which part of a house?
The basement
The basement collects radon because the gas is about eight times denser than air and seeps in through gaps in the foundation. Home test kits are hung on the lowest lived-in floor for that reason.
Q 03Radon is ranked the second-biggest cause of lung cancer in the United States, behind only what?
Smoking
Smoking is the only bigger cause, and the two are worse together, since radon is far riskier for people who also light up. The EPA links the gas to about 21,000 American deaths a year.
Q 04Radon levels run high above shale and which rock, a favourite for kitchen countertops?
Granite
Granite carries more uranium than most rocks, and that uranium slowly decays into radon. Even so, not every region built on the rock turns out to be a hot spot.
Q 05In 1971 a spacecraft detected radon seeping from the Aristarchus plateau on which world?
The Moon
The Moon gave itself away when Apollo 15 flew over Aristarchus and picked up a burst of radiation from decaying radon. The Lunar Prospector probe later pointed to the same gas from orbit.
Q 06Radon spikes in groundwater, seen before a 1966 Tashkent disaster, are studied as warnings of what?
Earthquakes
Earthquakes may open fresh fractures underground that flush trapped radon into wells before the ground shakes. The signal proved unreliable, though: many quakes arrived with no radon spike at all.
Q 07Which country's Misasa hot springs offer radon-rich baths and host a yearly Marie Curie festival?
Japan
Japan is home to Misasa, a spa town in Tottori Prefecture whose spring water gives off radon. Locals believe a soak is good for the health, though scientists have never agreed that it is.
Q 08Radon is invisible as a gas, but what does the element do once it is frozen solid?
It glows
It glows with a light that changes colour as it gets colder, powered by its own radioactivity. Liquid and solid radon are almost never seen, because that much of the element is so hazardous.
Q 09Radon's 'daughters' keep decaying until they settle as stable atoms of which heavy metal?
Lead
Lead is the end of the line, reached only after a chain of short-lived radioactive steps. Those solid in-between atoms, more than the gas itself, do the harm when they lodge in the lungs.
Q 10Early cancer doctors treated tumours with tiny 'seeds' of radon encased in which precious metal?
Gold
Gold held the radon in while letting its tumour-killing gamma rays out. Spent seeds were later sold and melted down, so some radioactive metal ended up in American jewellery.
Q 11Radon is the heaviest naturally occurring member of which family of elements?
Noble gases
Noble gases rarely react because their outer electron shells are full. Radon is the odd one out among the natural members: it has no stable form at all, so every atom of it is radioactive.
Q 12Which gas, used in camera flash lamps, sits directly above radon in the periodic table?
Xenon
Xenon is radon's upstairs neighbour, and radon reacts a little more readily than it does. Chemists rarely get to test that, because radon is too costly and too radioactive to experiment on.
Q 13Radon forms directly from the decay of which element, discovered by Marie and Pierre Curie in 1898?
Radium
Q 21Patients ride a train deep into a mountain to breathe radon near Bad Gastein, in which country?
Austria
Austria's Bad Gastein turned old mining tunnels into a clinic where guests lie inhaling radon. The idea came from miners who said their ailments eased underground.
Q 22In which US state do 'health mines' near the town of Basin sell time breathing radon for arthritis?
Montana
Montana's health mines draw people hoping that small doses of radon will ease their joints. Doctors discourage the practice, pointing to the well-documented harm that radiation does to the body.
Q 23Which US state has the highest average radon levels, thanks to glaciers that crushed Canadian rock?
Iowa
Iowa's rich farm soil is made of rock that glaciers scraped off the Canadian Shield and crushed to powder. Several of its cities have passed rules requiring radon-resistant construction in new homes.
Radium sheds a particle and becomes radon, so any rock holding one is always making the other. Radium itself descends from uranium, which is why uranium-rich ground gives off the gas.
Q 14Radon dissolved in a home's well water escapes into the air most readily during which activity?
Showering
Showering sprays and warms the water, the ideal conditions for shaking dissolved radon loose. Swallowing dissolved radon is rated a far smaller risk than breathing it in.
Q 15Which New Zealand-born physicist first detected radon in 1899 while working at McGill in Montreal?
Ernest Rutherford
Ernest Rutherford noticed a radioactive gas escaping from one of his samples, a find he shared with colleague Robert Owens. For decades the credit went instead to a German physicist who repeated the work a year later.
Q 16Before radon had a name, scientists called it by which word, from the Latin for 'to flow out'?
Emanation
Emanation was the label for decades, with a separate version named for each element that gave off the gas. Some chemists were still using the word as late as the 1960s.
Q 17Before 'radon' was adopted in 1923, the element was officially known by which name?
Niton
Niton was proposed in 1910 by the two chemists who first isolated the gas, because they found the older label awkward. It stayed official for about a decade before radon replaced it.
Q 18Which Scottish chemist, already a Nobel winner for finding argon and neon, isolated radon in 1909?
William Ramsay
William Ramsay and Robert Whytlaw-Gray collected enough radon to show it was the heaviest gas then known. Their melting-point figure, doubted since the 1920s, was backed up by computer simulations in 2018.
Q 19Radon's first compound was made in 1962 by combining it with which fiercely reactive element?
Fluorine
Fluorine is one of the few elements aggressive enough to grab hold of radon, forming a solid. The experiment is seldom repeated, since radon is costly and its compounds are dangerously radioactive.
Q 20Radon contaminates refinery pipes carrying which fuel gas, as the two boil at similar temperatures?
Propane
Propane and radon come off together when a refinery sorts crude oil by boiling point. As the radon decays inside the pipework, it leaves a coating of radioactive solids behind.
Q 24Which Native American nation supplied many Cold War uranium miners, who breathed radon unwarned?
Navajo
Navajo miners worked the Southwest's uranium belt in the 1950s, and their language had no word for radiation. Congress finally passed a law compensating people harmed by the radiation in 1990.
Q 25Radon atoms decay by firing out which radiation, blocked by skin but harmful inside the lungs?
Alpha particles
Alpha particles are too bulky to pass through tissue paper or skin, so radon outside the body does little harm. Breathed in, they hit delicate lung cells directly.
Q 26Roughly how long is the half-life of radon-222, the form of the gas that seeps into homes?
About four days
About four days is all it takes for half of any radon sample to vanish. That short life means a building clears within a few weeks once the source of the gas is removed or sealed off.
Q 27Which Swiss physician described a wasting disease of miners in the 1500s, long before radon was known?
Paracelsus
Paracelsus called the miners' illness mala metallorum. It was identified as lung cancer in 1879 among miners at Schneeberg in Germany, where radon gathered in the deep shafts.
Q 28Which common radon fix does the EPA warn against relying on by itself?
Sealing cracks
Sealing cracks leaves radon other ways in, so the EPA favours soil suction. That method uses a pipe and fan to draw the gas from under the house and release it above the roof.
Q 29Americans measure home radon in which unit, while most countries use becquerels per cubic metre?
Picocuries per litre
Picocuries per litre is the American yardstick, and one of them equals 37 becquerels per cubic metre. The EPA urges homeowners to act once a reading reaches 4.
Q 30The world's first radon spa opened in 1906 at Jáchymov, a mining town in which present-day country?
Czechia
Czechia's Jáchymov first grew rich on silver, and its Joachimsthaler coins gave the dollar its name. Its radon baths are offered for ailments from arthritis to skin disease.