55 Fun Facts About Carbon

What is carbon's atomic number?

6. That leaves four electrons in its outer shell, which is why carbon usually forms four bonds.

In diamond, each carbon atom's four bonds point to the corners of what shape?

Tetrahedron. That rigid network of strong bonds is why diamond is the hardest natural substance.

Coal formed mostly from the buried remains of what?

Ancient swamp plants. They rotted into peat, and millions of years of heat and pressure under buried sediment turned that peat into coal.

Carbon ranks where in abundance among elements in the universe by mass?

Fourth. Only hydrogen, helium and one heavier element outrank it, yet almost none of that carbon was made in the Big Bang.

By mass, which element is more plentiful in the human body than carbon?

Oxygen. Water makes up over half the body's weight, and water is mostly oxygen by mass.

Which form of carbon traps impurities in gas masks and water filters?

Activated charcoal. It is riddled with tiny pores, and impurities stick to all of that inner surface.

Graphite gets its name from a Greek verb meaning what?

To write. Thousands of years before it had that name, prehistoric potters in the Balkans painted their pots with it.

Graphite's carbon atoms bond in flat sheets; what holds those sheets together?

Van der Waals forces. They are weak, so the sheets glide past each other, which is why graphite works as a dry lubricant.

Why is 'diamonds are forever' technically untrue?

They should slowly turn into graphite, because graphite, not diamond, is carbon's most stable form at everyday conditions.

What is a two-dimensional sheet of carbon atoms in a hexagonal lattice called?

Graphene. Andre Geim and Konstantin Novoselov pulled one-atom-thick flakes of it off graphite using ordinary adhesive tape.

Buckminsterfullerene was named after an architect famous for designing what?

Geodesic domes. The discoverers thought the molecule's cage of hexagons and pentagons looked like one of Buckminster Fuller's domes.

Which honour did Curl, Kroto and Smalley win for discovering fullerenes?

The Nobel Prize in Chemistry. The find set off a wave of research into other new forms of carbon.

How many carbon atoms make up buckminsterfullerene, the best-known buckyball?

60. Clusters of 60 atoms proved unusually stable, which led their discoverers to deduce a closed, highly symmetrical cage.

Which carbon allotrope, found in 1997, is ferromagnetic and among the lightest solids at about 2 kg per cubic metre?

Its atoms are strung together in a loose 3D web of six- and seven-membered rings.

How was Q-carbon first made?

By firing a laser pulse at amorphous soot. The flash melts the carbon, which is then quenched so fast that the Q stands for 'quenched'.

Which material is the top candidate for the cable of a space elevator?

Carbon nanotubes. A Japanese builder has floated a nanotube space elevator by 2050, but the idea remains highly speculative.

What is the half-life of carbon-14?

About 5,700 years. Living things keep topping up their carbon-14, so the decay clock only starts once they die.

How is carbon-14 created?

Cosmic rays hitting nitrogen in the upper atmosphere make it, and 1950s and 1960s nuclear bomb tests nearly doubled the amount in the air.

Which chemist developed radiocarbon dating?

Willard Libby. To prove the method worked, his team tested it on ancient Egyptian artefacts whose ages were already known.

In 1988, radiocarbon labs in Arizona, Oxford and Zurich all tested samples from what?

The Shroud of Turin. Their tests dated its linen to between 1260 and 1390, centuries after the time of Jesus.

Which isotope did IUPAC adopt as the basis for atomic weights?

Carbon-12. Every relative atomic mass on a periodic table is still measured against it.

Carbon nuclei are forged in stars by which fusion route?

The triple-alpha process. Three helium nuclei must fuse almost at once, because the two-nucleus stepping stone, beryllium-8, falls apart instantly.

Why was no significant carbon created in the Big Bang?

It expanded and cooled too fast, so almost all the carbon around today was forged later, inside stars.

What is coal baked into, without air, to fuel iron-smelting blast furnaces?

Coke. It is strong enough not to be crushed by the ore piled above it, so hot gases can still rise through the furnace.

What colour does diatomic carbon, the gas that lights up many comets, glow when excited?

Green. The gas can't last at room temperature, quickly linking up into bigger carbon molecules.

Which element sits directly below carbon in the periodic table?

Silicon. It is a semiconductor, which is why most computer chips are built on it.

Carbon's ability to form long chains of carbon-carbon bonds is called what?

Catenation. It lets carbon build the long backbones of fuels, plastics and the molecules of life.

Which chemist showed in 1772 that diamond is carbon by burning it?

Antoine Lavoisier. His science was funded by a hated tax-collecting firm, and that job got him guillotined in the French Revolution.

Before Scheele's work, graphite had been widely thought to be a form of which metal?

Lead. That old confusion is why pencil cores are still called 'lead', though they hold none of the metal.

Which scientist, better known for his temperature scale, showed that iron becomes steel by absorbing a substance?

Réaumur. He also showed that some animals really can regrow limbs they have lost.

Which English valley's graphite was so pure and solid it could be sawn straight into sticks?

Borrowdale, Cumberland. Its graphite lined moulds for cannonballs, so the Crown took over the mine and guarded it.

Which odourless gas makes up most of natural gas?

Methane. Gas companies add mercaptan, which smells like rotten eggs, so that leaks can be noticed.

Natural diamonds are found in which volcanic rock?

Kimberlite. Digging into it during the diamond rush at Kimberley, South Africa, carved out the vast pit called the Big Hole.

Which country was the world's main source of diamonds for centuries, until the 1700s?

India. As its supplies ran low, newly discovered Brazilian diamonds took over the market.

Which mine, the world's main source of pink diamonds, closed in 2020 after 37 years?

The Argyle mine. At times it produced more diamonds by volume than any other mine, though few of them were gem quality.

Which American company announced in 1955 that its lab had made diamonds?

General Electric. Its scientists squeezed graphite under enormous pressure and heat, with a metal catalyst to help.

Before X-ray fluorescence, how were diamonds separated from crushed ore?

The final sorting steps are still done by hand.

Which US state has a park where visitors can dig for diamonds and keep what they find?

Arkansas. The search field is the eroded surface of an ancient volcanic crater that carried diamonds up from deep underground.

Carbon fibre is made by pyrolysing filaments of which polymer?

Polyacrylonitrile (PAN). Its filaments are stretched to line up the molecules before baking, which makes the finished fibre strong for its size.

What were the 61 tattoos on Otzi the Iceman made from?

Fireplace soot. Carbon stays put once it's in the skin, which is why the tattoos lasted some 5,200 years after his death.

Graphite serves what role in some nuclear reactors?

Neutron moderator. It slows neutrons, but energy stored in it can escape suddenly, and a botched attempt to release it set off Britain's Windscale fire.

Which grade of coal has the highest carbon content?

Anthracite. Extra heat underground drove off most of its volatile matter, leaving it at least 86% carbon.

Carbon combines with tungsten to form a carbide widely used for what?

Abrasives and hard cutting-tool tips. Carbide-tipped tools can cut metal far faster than tools made of high-speed steel.

Photosynthetic plants pull carbon dioxide from the air and build it into biomass in which named pathway?

The Calvin cycle. Melvin Calvin's Berkeley team mapped it by following radioactive carbon-14 through photosynthesis.

Which carbon allotrope has a hexagonal crystal lattice and properties similar to diamond?

It forms under some conditions where cubic diamond would normally appear.

Chalk, marble and which other common rock are mostly calcium carbonate?

Limestone. Much of it built up from the shells and corals of sea creatures, making it one of Earth's biggest stores of carbon.

Which isotope of carbon is used in NMR to study organic molecules?

Mass number 13. Its nuclear spin of one half lets NMR detect it, even though it is only about 1% of natural carbon.

Radiocarbon dating works on remains up to roughly what age?

About 50,000 years. Beyond that too little carbon-14 is left to measure, though special methods occasionally push further.

More than 20% of the carbon in the universe may be locked up in which class of compounds?

Polycyclic aromatic hydrocarbons. The 'PAH world' hypothesis suggests these ring molecules helped produce life's first building blocks.

How much carbon is estimated to be dissolved in all of Earth's water bodies?

About 36,000 gigatonnes, roughly 40 times what the atmosphere holds, and the open ocean keeps absorbing CO2 from the air.

Where in space have astronomers detected buckyball molecules?

In planetary nebulae. Ionised buckyballs also drift in the space between stars, where they absorb some of the starlight.

Where in the Solar System are carbon-rich asteroids relatively most common?

The outer asteroid belt. In 2020 Japan's Hayabusa2 brought home samples of Ryugu, a carbon-rich asteroid, holding organic compounds.

Which early electric light lit city streets from the late 1870s, before incandescent bulbs took over?

The arc lamp. Its light came from an electric arc between two carbon rods, which slowly burned away and needed adjusting.

Radioactive carbon-11 is used to label tracers for which kind of medical scan?

PET scans. Carbon-11 has a half-life of only about 20 minutes, so chemists must attach it to tracer molecules very quickly.

What is the German word for carbon?

Kohlenstoff. The name means 'coal substance', yet even the richest coal isn't pure carbon, while diamond and graphite are.