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Throughout the Christian Middle Ages, alchemists believed that man’s soul was divided in two after the fall of Adam and that if only it could be purified, then man would be reunited with God. They believed if they could uncover the secret of ‘purifying’ everyday materials into noble gold, then they would also discover the secret of purifying the soul.

Needless to say they didn’t work it out.

Among other things they made the mistake of assuming that everything in the universe was made up of four elements. Earth, water, air, and fire. This idea came from Aristotle, and it lasted for thousands of years. It took until 1789 for a French chemist to publish a treatise on thirty-three elements, which included oxygen, hydrogen, iron, and gold, and it formed the basis of modern chemistry.

Something I was delighted to find out is that modern chemistry has actually discovered the ancient secret of turning other metals into gold. You can read about it here, but you blast mercury with radiation so that it becomes unstable, and a small portion of it will decay into gold. The only catch is that the process costs way more than the gold’s worth, and that irradiating your soul won’t purify it, it’ll just give you cancer.

So far we’ve discovered one hundred and eighteen elements, or different types of atoms. The best way to categorise them is by the number of protons the atom has in its nucleus, which we call the ‘atomic number’, and we organise them with a weird grid called the periodic table.

The periodic table is usually thought of as a pretty boring thing. It conjures up high school, exams, and rote learning (at least it did for me) but it turns out it is one of the most powerful ideas that humanity has ever thought of.

It’s quite literally the framework of modern chemistry and materials science.

Image source: Wikipedia, Periodic Table Chart

It was invented by a Russian teacher called Dmitri Mendeleev as he was preparing a textbook for his class. He fell asleep and envisioned the complete arrangement of the elements in a dream.

“I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary.”

Dmitri Mendeleev

His genius was in recognising that properties of certain elements (like mass, freezing and boiling points, whether it’s hard or soft, or conducts electricity) repeated ‘periodically’ when you organised them by atomic number.

As soon as he wrote down his table (this was in 1869) he realised there were multiple elements yet to be discovered, and using his table he accurately predicted their properties.

Ever since the periodic table has helped us plan the creation of new chemicals and materials by telling us about the basic ‘building blocks’ involved. Volumes, properties, and reactivities are all clear at a glance.

But, something that the periodic table does not really show is that while each element has a fixed number of protons, the number of neutrons it has can vary.

These variants are called isotopes and they are fundamental in understanding elements, particularly man-made ones.

There tends to be a stable ratio of protons to neutrons, and if the ratio falls too far on either side, the atom will decay by emitting protons and neutrons as radiation until it becomes stable.

This is how we can create gold out of mercury – by bombarding it with so many neutrons that the ratio becomes unstable, and the mercury decays into gold.

To understand isotopes we need a different graph: one that shows not just every type of element, but every type of atom that is possible.

The best one I’ve found is the one below. The vertical axis is the number of protons (i.e. each row is a different element. Hydrogen is the first row, gold is number seventy-nineΒ etc.), and the horizontal axis is the number of neutrons.

The bluer it is, the more unstable the atom is.

When we split an atom in two in a nuclear explosion, it releases a ton of energy and usually forms atoms that don’t have a stable ratio. Both the explosion and the resulting waste emit radiation for tens of thousands of years. Because of its longevity, nuclear waste is almost guaranteed to be one of the lasting legacies of human civilisation.

Reddit, Table of all known elemental isotopes (nuclides) and their stabilities.


So atoms are made up of the same components, just different quantities of them. The quantities completely determine an atoms behaviour, from the volatile fluorine to the inactive neon.

Atoms like fluorine or caesium, which just have to gain or lose one atom respectively, are super reactive. They’ll tear electrons of other atoms to get what they want.

When you combine the two together, you get some otherworldly chemistry.

Atoms that have a complete outer shell, like neon, have no desire to donate or share any electrons. This keeps their charge neutral, so they rarely react with any other atoms at all.

While every atom occupies a unique place in the periodic table, as we move across it, patterns in behaviour emerge.

Chlorine is directly below fluorine, meaning it also has to gain just one electron. It is also reactive and dangerous but it’s heavier too, giving it behaviours that aren’t a copy of fluorine’s, but they do rhyme.

When atoms bond together to form molecules, their unique attributes create a huge array of molecules with their own attributes. These properties of atoms and molecules are responsible for much of the complexity of our world.

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Ben McCarthy

Ben McCarthy

Ben is the Founder of Discover Earth and the author of the Big Ideas Network.