The Origins of Krypton

Lucy Bell-Young

by Lucy Bell-Young

30th May 2018

Krypton isn’t just Superman’s home planet, it’s also one of the rarest gases in Earth’s atmosphere. Today marks the 119th birthday of krypton’s discovery by Sir William Ramsay and Morris Travers, so we thought we’d take a closer look at this elusive element.

What is Krypton (Kr)?

Before its destruction, Krypton was a planet that orbited a red star, boasted advanced technology and had huge crystalline structures across its lands – well, not exactly.

The inspiration and namesake for Superman’s home planet, krypton (Kr) is an inert and extremely rare gas that is found in the air. While it won’t make you powerful and isn’t used to form emerald green chunks of kryptonite, this element does have a very unique set of properties.

A Noble Gas

Krypton (Kr) is a member of the noble gases, a group of elements that are recognised for their extremely low chemical reactivity. These elements all belong to Group 18 of the periodic table. There are 6 noble gases that occur naturally:

  • Argon (Ar)
  • Helium (He)
  • Krypton (Kr)
  • Neon (Ne)
  • Radon (Rn)
  • Xenon (Xe)

Properties of Krypton

Unlike argon, which forms a considerable portion of the Earth’s atmosphere, krypton is very rare. Composing only 1 part per million of the atmosphere by volume, its name is directly related to its infrequent appearance: krypton is derived from the Greek word kryptos, meaning ‘the hidden one.’

The noble gases all share similar properties, and krypton is no exception. As a fellow noble gas, krypton is:

  • Monatomic
  • Odourless
  • Colourless
  • Tasteless
  • Mostly inert

Krypton is also three times heavier than air, which makes it heavier than other noble gases in the group. It is also slightly more reactive than some of the lighter gases and can form some chemical compounds.

A sideways picture of the periodic table

Krypton is one of the seven noble gases, which belong to Group 18 of the periodic table. These elements all have very similar properties, like being odourless, colourless and chemically inert.

Why Are Noble Gases Unreactive?

Historically known as the inert gases, Group 18 elements are especially noted for their unreactive nature. Although some of the gases have now been found to be slightly reactive under extreme conditions, they are still almost entirely chemically inert.

Noble gases are unreactive because they have a full outer shell of electrons. When elements have an unstable or incomplete outer shell, they will react with other substances to either gain or lose electrons. By having a stable arrangement, noble gases don’t need to react and, therefore, become chemically inert.

This is an extremely useful property to many industries that do not want a chemical reaction to take place. In deep-sea diving, for example, helium is used in breathing gas in order to prevent a reaction between oxygen, nitrogen and carbon dioxide which would be toxic.

Reactivity of Krypton

While krypton is mostly inert, it does actually react with fluorine gas to form krypton fluoride. This compound is a volatile and colourless solid that is often used in lasers. It is also a strong oxidising and fluorinating agent that can oxidise gold to its highest-known oxidation state.

Sir William Ramsay

Sir William Ramsay and Morris Travers discovered krypton on 30th May 1898. While this was a breakthrough discovery, it wasn’t the first noble gas Ramsay had identified – and it wasn’t the last.

A black and white photo of Sir William Ramsay, who discovered the noble gases

Sir William Ramsay discovered the noble gases between 1894 and 1910. This Scottish chemist found krypton by evaporating away all components of liquid air. This left behind a residue which Ramsay would later identify as krypton.

Discovering ArgonRamsay was a Scottish chemist who is known as the founder of the noble gases. In 1904, he received a Nobel Prize in Chemistry for “the discovery of the inert gaseous elements in air.”

Ramsay made his first discovery in 1894 when he and Lord Raleigh undertook an experiment where they successfully removed all known gases from air. This led them to find a monatomic, chemically inert gas that made up nearly 1% of the atmosphere. They called this argon.

Liberating Helium

The next noble gas Ramsay identified was helium. While the discovery of helium has been accredited to Sir Edward Frankland, who observed its yellow spectral line emanating from the chromosphere of the Sun, Ramsay was the first to show that it existed outside of the solar spectrum.

Discovering the Final 4  

On 30th May 1898, Sir William Ramsay and Morris Travers discovered the next noble gas when they boiled away all components of liquid air. This left behind a residue that would later be recognised as krypton.

Ramsay’s method of evaporating the components of liquid air not only led him to krypton, it also allowed him to isolate two more noble gases in the same year: neon and xenon.

The last of the Group 18 elements to be identified was radon, which Ramsay proved to be the sixth noble gas in 1910. Within 16 years, Sir William Ramsay had discovered an entire family of new elements.

What Are the Uses of Krypton?

Its rarity means that krypton is expensive, and therefore has limited use when compared to its other comrades. Helium, for example, has several applications across different industries.

Krypton is used to extend the life of the tungsten filament inside incandescent bulbs. This filament is what makes the bulb glow, and krypton is injected into the light-bulb in order to achieve this.

It is also sometimes used between the panels of double-paned glass. This is because its heavier weight helps to trap heat. However, argon is more commonly used for this because it is cheaper to obtain.

Cartoon picture of Superman

The noble gases are an important part of how we understand our world and the atmosphere around us. More importantly, if it wasn’t for Sir William Ramsay’s discovery 119 years ago, the names in the DC universe would be very different!


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