Hydrogen Trivia
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48 free Hydrogen trivia questions with answers — science & nature quiz, new questions added Sep 2026.
This hydrogen trivia quiz covers the lightest and most abundant element in the universe. The easy questions handle the basics: its symbol and atomic number, what its name means, what happens when it burns, and why it once lifted airships until the Hindenburg put a stop to that. The harder end digs into the chemistry and physics: the three isotopes and their names, why heavy water matters to nuclear reactors, tritium's half-life and its use in glowing watch dials, the ortho and para spin isomers, James Dewar liquefying it in 1898, the metallic phase thought to exist inside Jupiter, the 21-centimetre line astronomers use to map the cosmos, the Haber process, steam methane reforming, and how the first neutral atoms formed 370,000 years after the Big Bang. 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 helium quizzes are the natural next stop.
30 of 48 questions with answers and explanations. Play the quiz
Q 01What is hydrogen's atomic number?
1
1: the number counts the positively charged particles in an atom's nucleus, and hydrogen has a single one, making it the lightest element and earning it the first box on the periodic table.
Q 02Hydrogen is about three-quarters of the universe's ordinary matter by mass; which element makes up almost all the rest?
Helium
Helium is roughly a quarter of all ordinary matter. Every heavier element, from the oxygen you breathe to the iron in your blood, adds up to only about 2%.
Q 03Under standard conditions, hydrogen gas is made of molecules with which formula?
H2
H2: the bond between the two atoms is so strong that this famously flammable gas barely reacts at room temperature, until heat, a spark or a catalyst sets it off.
Q 04Which reclusive British scientist, who later 'weighed the Earth', identified hydrogen as a distinct substance in 1766?
Henry Cavendish
Henry Cavendish collected the gas bubbling off metals in acid and showed it was unlike any other air; he suspected he had bottled phlogiston, the supposed essence of fire.
Q 05What does the name 'hydrogen' mean?
Water-former
Water-former: the 1780s coinage joins the Greek for water to an ending meaning producing, because burning the gas makes water.
Q 06What was hydrogen gas called in the 1760s, before it got its modern name?
Inflammable air
Inflammable air was one of several 'airs' of the day: carbon dioxide was fixed air and oxygen dephlogisticated air. The clumsy labels gave way after 1787, when chemists renamed the elements.
Q 07Which chemist, who also named oxygen, gave hydrogen its name in the 1780s?
Antoine Lavoisier
Antoine Lavoisier coined the French word hydrogène. He paid for his laboratory by working as a royal tax collector, the job that sent him to the guillotine in 1794.
Q 08Which 17th-century scientist described in 1671 how iron filings in acid give off the gas now called hydrogen?
Robert Boyle
Robert Boyle, famous for his law of gas pressure, made the gas but took it for a kind of air; almost a century passed before anyone recognised it as a distinct substance.
Q 09Hydrogen's three natural isotopes differ only in their number of which particle?
Neutrons
Neutrons: ordinary hydrogen has none, deuterium one and tritium two. One extra neutron doubles the atom's mass, so deuterium compounds usually react more slowly than ordinary hydrogen's.
Q 10Deuterium and tritium are named from the Greek for second and third; what is ordinary hydrogen-1 formally called?
Protium
Protium comes from the Greek protos, first. It makes up more than 99.98% of all hydrogen, so in practice plain 'hydrogen' does the job and the formal name is rarely needed.
Q 11Nearly all the universe's deuterium was forged in what?
The Big Bang
The Big Bang made nearly all of it within its first few minutes, so the deuterium found in every glass of water is older than the Sun, the Earth and every star in the sky.
Q 12What is the name for H2O in which deuterium replaces ordinary hydrogen?
Heavy water
Heavy water is not radioactive and looks just like the ordinary kind. Canada's CANDU reactors are filled with it because it lets them run on natural uranium, with no enrichment needed.
Q 13Radioactive tritium keeps which of these glowing for years without power?
Exit signs
Exit signs filled with tritium gas glow for more than ten years with no wiring or batteries: the gas's decay lights a coating inside the tubes, so the way out still shows when the power fails.
Q 21Metallic hydrogen, a conductor formed at extreme pressure, is believed to exist deep inside which planet?
Jupiter
Jupiter squeezes hydrogen until it conducts electricity like a liquid metal, and NASA thinks the swirl of that layer as the planet spins is the dynamo behind its enormous magnetic field.
Q 22In which form does hydrogen exist inside stars?
Plasma
Plasma is gas so hot that its atoms are torn into electrically charged particles. NASA describes the Sun as a ball of it, with no solid surface anywhere.
Q 23Months after the Montgolfiers' hot-air flight, which French scientist, remembered for a gas law, launched the first hydrogen balloon in 1783?
Jacques Charles
Q 14Which American chemist, whose name is paired with Stanley Miller's in a famous origin-of-life experiment, discovered deuterium in 1931?
Harold Urey
Harold Urey found it by having litres of liquid hydrogen slowly boiled away until only a trace rich in the heavy atoms remained. The discovery won him the 1934 Nobel Prize in Chemistry.
Q 15Hydrogen atoms are small enough to seep into solid steel; what does that do to the metal?
Makes it brittle
Makes it brittle: steel loses its toughness once hydrogen soaks in, so pipelines and tanks that carry the gas have to be built from carefully chosen materials.
Q 16What is the antimatter counterpart of the hydrogen atom made of?
An antiproton and a positron
An antiproton and a positron make antihydrogen, the mirror image of the simplest atom. CERN builds these anti-atoms and holds them in magnetic traps, because a touch of ordinary matter annihilates them.
Q 17Hydrogen flames are hard to see in daylight because they emit mostly what?
Faint blue and ultraviolet light
Faint blue and ultraviolet light is all a hydrogen fire gives off: with no carbon in the fuel there is no glowing soot, the stuff that turns a candle flame yellow. Plants fit special flame detectors.
Q 18What are the two spin isomers of molecular hydrogen called?
Ortho and para
Ortho and para hydrogen differ in whether the two nuclei spin the same way or opposite ways. Room-temperature gas is about 75% ortho, and its slow flip to para gives off enough heat to boil stored liquid hydrogen away.
Q 19Which Scottish scientist, inventor of the vacuum flask, first liquefied hydrogen in 1898?
James Dewar
James Dewar never patented his vacuum flask, so when a German firm began selling it as the Thermos in 1904 he earned nothing from the invention that had kept his hydrogen liquid.
Q 20Hydrogen turns liquid only when chilled to within about 20 degrees of what?
Absolute zero
Absolute zero is −273 °C and hydrogen liquefies at about −253 °C, so it is stored in heavily insulated tanks, and even then some is steadily lost as the liquid boils off.
Jacques Charles launched his unmanned balloon of rubber-coated silk from Paris that August. It drifted some 20 km to the village of Gonesse, where terrified peasants attacked it and tore it apart.
Q 24At about 7% of air's density, hydrogen still routinely lifts which of these?
Weather balloons
Weather balloons are often filled with hydrogen. Each swells from about 1.5 m across to more than 6 m as the air thins, can climb past 30 km before it bursts, and drops its instruments by parachute.
Q 25Which hydrogen airship burned over New Jersey on 6 May 1937, ending commercial airship travel?
The Hindenburg
The Hindenburg was destroyed in little more than half a minute, yet 62 of the 97 people on board survived. Thirty-five of those aboard and one man on the ground were killed.
Q 26Which Hungarian-born physicist, who worked under Oppenheimer at Los Alamos, is known as the father of the hydrogen bomb?
Edward Teller
Edward Teller had pressed for the weapon since his Los Alamos days, and after the Soviet atomic test of 1949 he helped persuade President Truman to build it. The first was exploded in the Pacific in 1952.
Q 27In the Bronsted-Lowry theory, acids are defined as donors of what?
Protons
Protons are all that is left when a hydrogen atom loses its single electron, so to a chemist 'hydrogen ion' and 'proton' mean the same thing. In water each one instantly latches on to a molecule, making H3O+.
Q 28What is the negatively charged hydrogen ion, H-, called?
Hydride
Hydride forms when a hydrogen atom takes a second electron from a reactive metal such as sodium or lithium. It is a ferociously strong base: chemists use sodium hydride to pull hydrogen off molecules that nothing milder will touch.
Q 29When the first hydrogen atoms formed, which still-detectable glow was set free?
Cosmic microwave background
The cosmic microwave background is that first free light. Until atoms formed, the universe was an opaque fog of loose electrons; once it cleared, light streamed out, and expansion has since stretched it into faint microwaves.
Q 30Radio astronomers map cosmic hydrogen using an emission line at what wavelength?
21 centimetres
21 centimetres is a radio wavelength, first picked up in 1951, that passes straight through the dust clouds that block starlight. It lets astronomers map our galaxy's hydrogen where optical telescopes see only darkness.