Carbon
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Carbon

Carbon is the element that forms the backbone of all long, complex molecules and as a result, makes up about 18% of your body.

Like many elements, it was created within the core of a star and was expelled into space before finding its way down to Earth.

Carbon’s importance comes from two attributes. The first is that it’s the most common element whose atoms have four electrons in their outer shell.

This means that carbon can form up to four bonds with other atoms. It’ll often use two of them to form bonds with other carbon atoms, creating long chains while having two bonds left over to interact with other atoms.

This opens the door for an extraordinary range of possible compounds, and makes it by far the most important element for all known forms of life. It also has an entire branch of chemistry to itself called ‘organic chemistry’.

Here are some examples of simple carbon chains.

Each ‘C’ is a carbon atom, and each ‘H’ is a hydrogen atom. Carbon can form long complex molecules to create substances with unique properties.
Each ‘C’ is a carbon atom, and each ‘H’ is a hydrogen atom. Carbon can form long complex molecules to create substances with unique properties.

It doesn’t take too much imagination to picture enormously complicated molecules strung together with carbon like in the image below.

Long, interlinked carbon chains. Each dark grey ball is a carbon atom, and each white ball is a hydrogen atom.
Long, interlinked carbon chains. Each dark grey ball is a carbon atom, and each white ball is a hydrogen atom.

Chains with different shapes create substances with totally different attributes. Carbon forms graphite, diamonds, carbon nanotubes, and many other substances just by arranging its own atoms differently.

A diamond and a lump of graphite, commonly used for pencil lead.
A diamond and a lump of graphite, commonly used for pencil lead.

These are called different ‘allotropes’ of carbon, meaning they are both made from the same material but the atoms have arranged themselves in different ways.

The different structures made by carbon.
The different structures made by carbon.

We’ve discovered over 10 million types of carbon molecules (more than any other element) but it’s estimated that this is just a fraction of the total possible number.

This huge range of molecules is the basis of life as we know it, and it is why life is said to be ‘carbon-based’.

For example, carbon chains are the backbone of essential molecules like carbohydrates, fats, sugars, proteins, alcohols, as well as DNA and RNA.

For such an important element, it’s fortunate that it is so abundant. The ‘carbon cycle’ is what we call the movement of carbon across the Earth, often moving from one molecule to the next and through countless living creatures over millions of years.

When a sapling plant grows, it needs carbon to make sugars, DNA, and other molecules for its new branches and leaves. So it will absorb carbon dioxide out of the air through its leaves, reconfigure it into the molecules it needs, and keeps growing. Most of the mass of a plant comes out of the air in this way.

Forests like this Redwood forest are huge carbon ‘sinks’, pulling carbon dioxide out of the atmosphere and into their bodies.
Forests like this Redwood forest are huge carbon ‘sinks’, pulling carbon dioxide out of the atmosphere and into their bodies.

When an animal eats a plant it absorbs its sugars and other molecules, breaks some of them down, and exhales carbon dioxide. When you exercise and lose a few kilograms of fat, most of it is exhaled as carbon dioxide.

Carbon travels extensively across the Earth, through the atmosphere and oceans just as easily as through plants and animals. It is one of the crucial ingredients that makes Earth an oasis for life.

Earth’s carbon cycle.
Earth’s carbon cycle.