Lanthanum
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40 free Lanthanum trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Lanthanum is element 57, the metal that gives the whole lanthanide row its name, and one of the most useful elements most people have never heard of. It turns up in hybrid cars, studio lights, telescope glass, medicine cabinets and even a top-secret wartime experiment. This quiz turns the best lanthanum fun facts into multiple-choice questions: where the name comes from, who found the element and how, how the soft silvery metal behaves in air and water, where it is mined, and the surprising jobs it does in modern technology. Every answer comes with a short explanation, so you get the story behind each fact. It suits chemistry students revising the periodic table, teachers looking for an element-of-the-week activity, and anyone who enjoys a good science fact to share.
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Q 01Lanthanum's name comes from an ancient Greek word with which meaning?
To lie hidden
To lie hidden fits: lanthanum sat unnoticed for decades inside a mineral that chemists believed held only one new element.
Q 02The 2008 model of which hybrid car carried 10 to 15 kilograms of lanthanum in its rechargeable battery pack?
Toyota Prius
Toyota Prius batteries store their charge in a lanthanum-rich alloy, usually a cheap blend with other rare earths in place of the pure metal.
Q 03RaLa, short for radioactive lanthanum, was a series of implosion tests begun during which secret wartime program?
Manhattan Project
Manhattan Project scientists used the blasts to perfect the implosion that squeezes a plutonium bomb's core; a history of the work called RaLa the most important single experiment for the final design.
Q 04The parent isotope that steadily produced radioactive lanthanum for RaLa tests was nicknamed after which farm animal?
A cow
A cow was the nickname because fresh radioactive lanthanum could be 'milked' from it again and again as the parent isotope decayed.
Q 05Mischmetal, an alloy that is roughly a quarter lanthanum, is best known as a key ingredient of which pocket item?
Cigarette lighters
Cigarette lighters strike their sparks from a 'flint' that is really mischmetal hardened with iron and magnesium oxides.
Q 06Lanthanum carbonate, a phosphate-binding medicine for people, has also been sold by Bayer Animal Health for which pets?
Cats
Cats can suffer the same build-up of phosphate in the blood as people, and the feline version went by the trade name Renalzin.
Q 07Although it is called a rare earth, lanthanum is almost three times as abundant in Earth's crust as which metal?
Lead
Lead is the scarcer one; rare earths got their label because few deposits were known at first and mining them is slow and costly.
Q 08Lanthanum gives carbon arc lamps a sunlight-like glow, which once made the element a staple of which industry?
Movies
Movies were once shot and projected by carbon arc light, a job that swallowed about a quarter of all rare-earth compounds produced.
Q 09Lanthanum carbonate, sold as Fosrenol, treats high blood phosphate in patients with chronic disease of which organs?
Kidneys
Kidneys that are failing cannot clear phosphate, so the drug traps it in food; the tablets are so large that they are meant to be chewed.
Q 10Small amounts of lanthanum in many swimming pool products strip out the phosphates that feed which unwanted growth?
Algae
Algae starve without phosphate, and the same trick is used on whole lakes, where a lanthanum-laced clay locks the nutrient into an inert mineral.
Q 11Lanthanum oxide gives glass a high refractive index and low dispersion, which makes it prized for making what?
Camera lenses
Camera lenses and telescope lenses both rely on lanthanum glass, and the oxide also helps the glass resist attack by alkalis.
Q 12Early gas mantles made with lanthanum oxide in the 1880s sold poorly and gave off light with which tint?
Green
Green-tinted light did the mantles no favors, and the company that Auer von Welsbach founded to make them failed in 1889.
Q 13Lanthanum's oxide coating does not shield the metal beneath but flakes off like which familiar product of corrosion?
Rust
Rust is the usual comparison: a centimeter-sized lump of lanthanum left in air corrodes away completely within a year.
Q 21A lanthanum-based ceramic discovered in 1986 won a Nobel Prize as the first high-temperature example of which material?
Superconductor
Superconductor is the word: the black lanthanum-copper oxide carried current with no resistance at a then unheard-of temperature, and its finders shared the 1987 physics Nobel.
Q 22Lanthanum has no known role in the human body, but which organisms from hot volcanic mud use it to grow?
Bacteria
Bacteria found in volcanic pools near Naples use lanthanum in an enzyme that helps them feed on methane gas, though a few sister elements can stand in for it.
Q 23Lanthanum was first detected in the 1830s as an impurity in a nitrate of which more abundant rare-earth metal?
Cerium
Q 14Lanthanum 'sponge' alloys can reversibly soak up as much as 400 times their own volume of which gas?
Hydrogen
Hydrogen goes in and out on demand, and the alloy gives off heat every time it fills, which interests designers of energy-saving systems.
Q 15Lanthanum was discovered in a heavy mineral dug from the Bastnäs mine, which is in which Nordic country?
Sweden
Sweden's Bastnäs mine had been puzzling chemists since 1751, when a mineralogist first noticed the unusually heavy stone there.
Q 16Bayan Obo, a massive deposit of the lanthanum ore bastnäsite and the largest rare-earth find yet, is in which country?
China
China's Bayan Obo mines, in Inner Mongolia, were turning out 45% of the world's rare earths by 2005.
Q 17Mischmetal, a rare-earth alloy rich in lanthanum, takes its name from which language's words for mixed metal?
German
German gave it the name Mischmetall; its inventor devised the alloy while hunting for uses for the rare earths left over from making gas mantles.
Q 18Adding a little lanthanum makes which common alloy more malleable, more ductile and better at resisting impact?
Steel
Steel toughens with tiny doses, while lanthanum added to molybdenum does a different job, making that metal less hard.
Q 19Lanthanum compounds go into the cracking catalysts that oil refineries use to turn heavy crude into which product?
Gasoline
Gasoline is the prize: by 2006 some 400 refineries ran these cracking units, which handle about a third of the crude oil those plants refine.
Q 20Cathodes made of lanthanum hexaboride feed electrons to Hall-effect thrusters, a kind of ion engine that propels what?
Spacecraft
Spacecraft are not the only users: the same hot crystals supply the beam in electron microscopes, where they outlast and outshine tungsten.
Cerium nitrate was roasted in air and then treated with dilute nitric acid, a simple routine that teased out the oxide of a new element.
Q 24Which alkaline earth metal, element 56, sits immediately before lanthanum in the periodic table?
Barium
Barium is also lanthanum's parent in a sense: radioactive barium-140 decays into lanthanum-140, the isotope used in wartime implosion tests.
Q 25Lanthanum oxide is added to tungsten welding electrodes as a safer substitute for which radioactive element?
Thorium
Thorium gives welders excellent arcs that start easily, but its dust and vapors are a health risk, hence the switch.
Q 26Which chemist found lanthanum in the 1830s but hesitated to announce it for fear of embarrassing his mentor?
Carl Gustaf Mosander
Carl Gustaf Mosander trained as a pharmacist and physician, and his find showed that an 'element' his own teacher had discovered was really a mixture.
Q 27In chemical reactions, lanthanum usually gives up three electrons to reach the stable configuration of which noble gas?
Xenon
Xenon has 54 electrons, three fewer than lanthanum, so shedding three leaves the colorless La3+ ion found in nearly all of its compounds.
Q 28Lanthanum oxide reacts with water so eagerly that it gives off plenty of heat along with what else?
A hissing sound
A hissing sound comes off as the white powder turns into lanthanum hydroxide, which then goes on to soak up carbon dioxide from the air.
Q 29Lanthanum hexaboride, a ceramic almost as hard as diamond that is used in hot cathodes, is which striking color?
Purple
Purple-violet crystals of the compound rate 9.5 on the Mohs hardness scale and melt only at 2,210 °C.
Q 30Lanthanum is an essential ingredient of ZBLAN, a heavy glass whose optical fibers excel at carrying which radiation?
Infrared
Infrared light passes through ZBLAN unusually well, and a 1998 study showed that making the glass in zero gravity leaves fewer flaw-causing crystals.