Oganesson (Og)

Quick reference

The end of the periodic table (so far)

Oganesson is element 118, the heaviest element ever made. It sits at the very end of the seventh row of the periodic table. Its discovery completed the seventh row, so every spot in the first seven periods is now filled.

How it was made

Oganesson doesn’t exist in nature. It’s a superheavy element, made one atom at a time in a particle accelerator.

Scientists at the Joint Institute for Nuclear Research in Dubna, Russia, working with Lawrence Livermore National Laboratory in California:

1. Prepared a target of californium-249 (element 98).
2. Fired a beam of calcium-48 ions (element 20) at it for months.
3. Very rarely, a calcium nucleus fused with a californium nucleus: 98 + 20 = 118 protons.

The atoms decayed within about a millisecond. Scientists identified oganesson by detecting the chain of decay products it left behind.

Naming oganesson

New elements must be confirmed by IUPAC (the International Union of Pure and Applied Chemistry) and IUPAP before being named.

• Before being named, element 118 was called ununoctium (Latin-Greek for "one-one-eight"), with the temporary symbol Uuo.
• In 2016, IUPAC officially named it oganesson after Yuri Oganessian, who led much of the research on superheavy elements.
• It’s only the second element named after a living person, after seaborgium (element 106, named after Glenn Seaborg).
• The ending "-on" matches other elements in group 18: neon, argon, krypton, xenon and radon.

Four new elements were named that year: nihonium (113), moscovium (115), tennessine (117) and oganesson (118).

Is it really a noble gas?

Oganesson is placed in group 18 with the noble gases, like helium, neon and argon. Those elements are usually gases and very unreactive because their outer electron shells are full.

But scientists predict oganesson may break the pattern:

This happens because of relativistic effects. In very heavy atoms, the large positive charge of the nucleus makes inner electrons move at a significant fraction of the speed of light. According to Einstein’s relativity, this changes how electrons behave, altering the element’s chemistry.

No one has been able to test oganesson’s chemistry directly, because only a few atoms have ever existed, and each lasted less than a millisecond.

The island of stability

Generally, the heavier an element, the less stable it is. But scientists predict an island of stability: certain superheavy nuclei with "magic numbers" of protons and neutrons might last much longer, perhaps minutes, days or even longer. Finding them is one goal of superheavy element research.

What’s next?

Scientists are trying to make elements 119 and 120, which would begin an eighth row of the periodic table. This requires even more powerful beams and new target materials, and might take years of continuous experiments.

Uses

Oganesson has no practical uses outside research, because only a few atoms have ever been made and they decay almost instantly. Its value is scientific: it helps test our understanding of atoms, nuclear forces and the limits of the periodic table.

Common mistakes

• Thinking oganesson was found in nature. It was made in a lab.
• Assuming it behaves like other noble gases. Relativistic effects may make it very different.
• Thinking scientists have a sample you could see. Only a few atoms have ever existed.

Try it yourself

1. Find oganesson on the periodic table. What group and period is it in?
2. Add the atomic numbers of calcium and californium. What do you get?
3. List the four elements named in 2016 and where each name comes from.

(Answer to 2: 20 + 98 = 118)

Quick recap

• Oganesson (Og, atomic number 118) is the heaviest element known.
• It was made by fusing calcium-48 with californium-249; only about five atoms have been detected.
• It was named in 2016 after physicist Yuri Oganessian.
• It’s in group 18 but may be a solid with unusual chemistry because of relativistic effects.
• Its half-life is less than a millisecond, so it has no practical uses.