60 Fun Facts About Carbon

What is carbon's atomic number?

Its symbol is C and it sits in group 14 of the periodic table with silicon and germanium.

Carbon is described as tetravalent. How many covalent bonds can each atom form?

Its outer shell holds four electrons, which is why it builds such an enormous variety of molecules.

The name carbon comes from the Latin word for what?

German, Dutch and Danish are blunter still: Kohlenstoff, koolstof and kulstof all mean 'coal-substance'.

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

Only three lighter elements outweigh it; more than 20% of cosmic carbon may be tied up in polycyclic aromatic hydrocarbons.

Carbon is the second most abundant element in the human body by mass. Which element comes first?

Most of that oxygen is in water, while carbon forms the backbone of proteins, fats, sugars and DNA.

Under normal conditions, which three carbon materials have the highest thermal conductivities known?

Diamond is also the hardest natural material known, yet it barely conducts electricity.

Graphite gets its name from a Greek verb meaning what?

It is soft enough to leave a streak on paper because its hexagonal sheets slide past one another.

In graphite, each carbon atom is bonded to how many others within its flat sheet?

The sheets stack loosely through weak van der Waals forces, which is why graphite is soft and slippery.

Why is 'diamonds are forever' technically untrue?

At high temperatures the change happens fast; diamonds can burn up in a house fire.

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

As of 2009 it appeared to be the strongest material ever tested, though separating it cheaply from graphite is still a challenge.

Fullerenes and buckyballs are named after which architect?

His geodesic domes resemble the molecules' structure; the best-known buckyball is the soccerball-shaped C60.

Fullerene was discovered in 1985. Its discoverers Curl, Kroto and Smalley won which honour in 1996?

The find revived interest in new allotropes and led to glassy carbon and the realisation that 'amorphous' carbon is not truly amorphous.

How many atoms are in buckminsterfullerene, the simplest and best-known buckyball?

Its cells include pentagons as well as hexagons, which warps the sheet into a sphere.

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.

Q-carbon, announced in 2015 by a North Carolina State University team, was made how?

It reportedly shows ferromagnetism, fluorescence and hardness greater than diamond.

Linear acetylenic carbon, or carbyne, has a Young's modulus roughly how many times that of diamond?

It is a polymer of alternating single and triple bonds, of great interest to nanotechnologists.

What is the half-life of carbon-14?

That is why it is virtually absent from ancient rocks and useful for dating things only up to about 40,000 years old.

How is carbon-14 created?

Thermal neutrons collide with nitrogen-14 nuclei at altitudes of 9 to 15 km, producing carbon-14 and a proton.

In what year was radiocarbon dating invented?

It works because carbon-14 in a body stays roughly constant in life and then declines predictably after death.

What percentage of the carbon on Earth is the isotope carbon-12?

Almost all the rest is carbon-13, the isotope chemists use for NMR; living things skew even further toward carbon-12.

In 1961, IUPAC adopted which isotope as the basis for atomic weights?

Before that, oxygen had served as the reference standard.

Carbon nuclei are forged in stars by which fusion route?

Three helium nuclei must collide almost at once, because the two-step intermediates lithium-5 and beryllium-8 fall apart instantly.

Why was no significant carbon created in the Big Bang?

The process needs temperatures above 100 megakelvins and a helium concentration the young universe never sustained.

Carbon has the highest sublimation point of any element. Roughly what is it at atmospheric pressure?

It has no melting point at normal pressure at all; its triple point is at about 10.8 MPa and 4,600 K.

What colour does diatomic carbon gas (C2) glow when excited?

That green glow is what you see in the heads of comets and in a hot flame's inner cone.

Roughly how many carbon compounds have been described and indexed?

That is still only a fraction of what is theoretically possible; more known compounds contain carbon than do not.

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

It is the reason organic chemistry is effectively boundless.

Which chemist showed in 1772 that diamond is carbon by burning it and finding it gave off the same gas as charcoal?

He later listed carbon as an element in his 1789 textbook.

Before Scheele's work in 1779, graphite had been widely thought to be a form of which metal?

That confusion is why we still call pencil graphite 'lead'; Scheele showed it was charcoal with a little iron mixed in.

Who demonstrated in 1722 that iron becomes steel by absorbing some substance, later identified as carbon?

Réaumur is better known for his thermometer scale.

Which English valley's graphite was so pure that pencils were made by sawing it into strips?

Until the 19th century, the strips were simply encased in wood; today graphite is combined with clay to make pencil 'lead'.

Vein or lump graphite, the rarest and most valuable type, is only commercially mined in which country?

China dominated world graphite output in 2010 with 800,000 of 1.1 million tonnes.

Natural diamonds are found in which volcanic rock?

It occurs in ancient volcanic 'necks' or 'pipes', most notably in southern Africa.

Which country led the world in diamond production from about the 9th century BC to the mid-18th century?

Its alluvial deposits were exhausted by the late 1700s, when Brazil took over after finds in 1725.

Which Australian site was the world's top diamond source, producing 14 million carats in 2018?

Ekati and Diavik are in Canada, and Mir and Udachnaya are in Russia's Yakutia.

Roughly what share of mined diamonds are unsuitable as gems and relegated to industrial use as 'bort'?

That is about 100 million carats a year, dwarfed by the 3 billion carats of synthetic diamond made annually.

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

The final sorting steps are still done by hand.

Which US state, along with Colorado and Montana, has yielded natural diamonds?

A microscopic diamond found in 2004 led to bulk sampling in remote Montana in 2008.

Carbon fibre is made by pyrolysing filaments of which polymer?

The result has a higher specific tensile strength than steel and reinforces lightweight composites.

Which pigment was probably one of the first used for tattooing, and survives on Ötzi the Iceman?

His carbon tattoos lasted his lifetime and 5,200 years after his death.

Graphite serves what role in some nuclear reactors?

Stored Wigner energy can release suddenly; a botched annealing set off the Windscale fire.

Carbon monoxide is dangerous because it binds permanently to which molecule in the blood?

It displaces oxygen, which has a lower binding affinity; the gas is colourless and odourless.

Anthracite, the richest coal, contains roughly what percentage of carbon?

Coal reserves total around 900 gigatonnes, about 80% of all fossil fuel.

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

Iron carbide, cementite, is the hardening phase in steel.

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

This carbon fixation is one loop of the wider carbon cycle that runs through animals, oceans, coal and oil.

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

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

How many isotopes of carbon are known in total?

The shortest-lived, carbon-8, decays by proton emission with a half-life of 3.5×10⁻²¹ seconds.

Which exotic isotope of the element shows a 'nuclear halo', with a radius far larger than expected?

A halo nucleus is one whose outer nucleons orbit well beyond a normal dense core.

Which isotope of the element is used to identify it in NMR experiments?

It makes up just 1.07% of natural carbon, and living things discriminate against it in their biochemistry.

Up to roughly what age can radiocarbon dating be used?

Carbon-14 is virtually absent from ancient rocks because of its short half-life.

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

NASA upgraded its PAH database in 2014; the compounds feature in a hypothesis about the origin of life.

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

The atmosphere holds about 900 Gt and the biosphere roughly 550 Gt, with big uncertainty over deep-subsurface bacteria.

Roughly what share of US industrial diamonds are manufactured rather than mined?

Natural deposits lie mainly in Africa, with others in Arkansas, Canada, the Russian Arctic, Brazil and Australia.

At what altitudes is carbon-14 formed by cosmic rays hitting nitrogen-14?

Thermal neutrons strike nitrogen nuclei, yielding carbon-14 and a proton.

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

None has yet been directly sampled, and space-based carbon mining remains hypothetical.

Which heavier analogue of cyanide, with a phosphorus atom, is also classed as inorganic?

Cyanide behaves much like a halide ion and can pair up into cyanogen, (CN)₂.

In carboranes, a carbon atom is bonded to how many boron atoms?

They are stable dodecahedral derivatives of the B₁₂H₁₂²⁻ unit with one BH replaced by CH⁺.

The nitrogen-fixing FeMoco cofactor in microbes has a carbon atom bonded to how many iron atoms?

The hexamethylbenzene dication was confirmed in 2016 to contain a six-bonded carbon too.

Which three French scientists confirmed in 1786 that graphite was mostly carbon and proposed the name 'carbone'?

Lavoisier then listed carbon as an element in his 1789 textbook.

What is the German word for carbon, which literally means 'coal-substance'?

Dutch koolstof and Danish kulstof carry the same meaning; the English word comes from Latin carbo.