The International Union of Pure and Applied Chemistry (IUPAC) has announced that four new elements — with atomic numbers of 113, 115, 117, and 118 — will be added to the periodic table.

This is a big deal, since these four elements — all super heavy, lab-made, and very radioactive — complete the unfilled spaces on the seventh row of the periodic table. Their discoveries also open the door for scientists to create even heavier, perhaps useful, synthetic elements in the future.

Here, we break down what the discoveries mean (that is, other than the fact that people who have periodic table tattoos will now be out of date).

These four new elements don't exist naturally

Every element is given an atomic number, which corresponds to the number of protons in its nucleus. Hydrogen, the lightest element, has an atomic number of one, and its nucleus contains one proton. Element No. 2 — helium — has two.

These new elements have 113, 115, 117, and 118 protons respectively. Atoms with that many protons are too unstable to exist in nature. That's because protons naturally repel one another. In smaller atoms, the strong nuclear force — the powerful energy that is unleashed in a nuclear explosion — keeps the protons bonded. But in larger atoms, it loses its grip, and the atoms decay into more stable elements with fewer protons.

(Uranium, with 92 protons, is the heaviest element to exist naturally.)

How to create new, heavier elements: smash together lighter ones

Elements with very high atomic numbers have to be created by smashing together two smaller atoms in the hope that some of their protons stick together.

"To create 117," Scientific American explains, "the researchers smashed calcium nuclei (with 20 protons apiece) into a target of berkelium (97 protons per atom)." But this is much harder than it sounds. Berkelium (named after Berkeley, California) is extraordinarily rare; it took the team more than two years to stockpile 13 milligrams of it for the purpose of the experiment.

Once created, element 117 almost instantaneously decays and disappears. It has a half life (the amount of time it takes for half a given amount of the element to decay) of fifty-thousandths of a second. Element 113 — created by bombarding bismuth with zinc ions — is also fleeting: It decays in less than a thousandth of a second, its Japanese discoverers report.

And to be clear, these elements weren't just discovered. Labs have had evidence of their existence for years. But IUPAC has a lengthy process to verify claims.

What's the point of discovering new elements?

So why prove the existence of these barely there elements with no apparent practical value? One, because we can. It's important to prove scientific theories with observational data. It strengthens further predictions we can make off the periodic table.

Two, because we may, one day, create some very heavy, very useful new elements.

Quantum theory posits that it may be possible to create extremely heavy elements — with more than 120 protons — that are also very stable (meaning they'd resist decay). These elements would exist in an "island of stability" at the end of the periodic table, and no one knows what properties they might have.

What will we call these new elements?

IUPAC credits a joint Russian-American team with the discovery of 115, 117, and 118, and a Japanese team with the discovery of 113. "To scientists, this is of greater value than an Olympic gold medal," Ryoji Noyori, a Nobel Prize winner, explained to the Guardian. The discoverers get to name the elements.

"New elements can be named after a mythological concept, a mineral, a place or country, a property, or a scientist, and will be presented for public review for five months before a final decision about the new official name and symbol is made," Science Alert reports.

A quick refresher on the periodic table

This is the periodic table of the elements. It describes the weight and chemical properties of all the known elements in the universe.

It follows these rules (generally, although there are many exceptions).

Going from left to right across the periodic table, elements are arranged by:

lighter to heavier

more metallic to less metallic

more positively charged to more negatively charged to inert (neither positively or negatively charged)

The genius of the periodic table is that its inventor, Dmitri Mendeleev, discovered that as elements grow heavier, this pattern repeats itself. Each time the pattern repeats, a new row forms.

The result is a table that allows a person to both easily scan the weight of elements and also guess at how they will react with other elements on the table. So we know that chemically, sodium (symbol Na) acts a lot like potassium (symbol K), even though potassium is nearly double the weight of sodium. And so on.