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Krypton – Discovery, Source, Physical Properties, Chemical Properties, Toxicity, Applications, Practice Problems and FAQ

Who wouldn’t love to take a trip to an alien planet and explore some of its encrypted secrets and mysteries? Imminently, the excitement of such a voyage would be tripled if you learn that it’s the home planet of your favourite and the iconic superhero, “The Superman”! And many of you would know the name of it as well. Yes, it is the fictional planet called “Krypton”!

Krypton, not the fictitious planet you might associate with Superman, but the chemical element that actually gave his world its name, was found on May 30, 1898.


In a comic book that was released in June 1938, Superman's home planet was first mentioned, forty years after the discovery of Krypton, the chemical element.

The name Krypton was chosen for the planet for a multitude of reasons, including its enigmatic nature, the element's brilliance, and simply how amazing it sounds.

Wish to learn more? Why not get up and get moving!


Krypton - Discovery 

William Ramsay, a Scot, along with his English student Morris Travers, were looking for gases in the helium family in the 19th century. The two British scientists thought that a lighter substance may fill the space left between helium and argon in the Periodic Table.

In that sense, it was an accident that they were discovered. In their procedure, the water, nitrogen, oxygen, helium, and argon were removed from a sample of liquified air by boiling it, then they looked for a lighter element that they thought would replace the void.

However, the researchers went overboard with the evaporation and only collected a heavy gas sample.

With the use of an induction coil and a Plucker tube, the residue was used to create a spectrum with vivid yellow and green lines. When the light spectrum was analysed, it revealed that it belonged to an unidentified element. On May 30, 1898, a real substance had been found that would later serve as the basis for fiction.

Ramsay and Travers named element number-36, Krypton, after the Greek word for Kryptos which meant "hidden”, because they had to search for it by removing everything else. It turned out to be appropriate because, at one part per million by volume, it is actually concealed in the earth's atmosphere. Ramsay won the chemistry Nobel Prize in 1904 for playing a significant role in the discoveries of helium, argon, xenon, and radon.

Krypton - Origin and Source

Krypton occurs naturally in minute amounts in minerals and meteorites. A concentration of roughly (1 cm3/m3) naturally occurs in the atmosphere of Earth. Little amounts of radioactive Krypton-85 are found in the environment because of the fission of uranium and other actinides that occur naturally and as a result of neutrons. Due to interactions between stable krypton isotopes and neutrons from cosmic rays, Krypton-81 and Krypton-85 are both present in the atmosphere. Byproducts from the liquefaction and separation of air can include Krypton.

Nuclear fission is Krypton-85's main source of production. When an atom of Uranium-235 (or another fissile nuclide) divides into two big fragments, fission products with masses between 90 and 140, and two or three neutrons are obtained. The split usually occurs asymmetrically. The total number of protons and neutrons in an atom's nucleus is known as the mass number. One such fission product is Krypton-85, which has a fission yield of roughly 0.3 %. In other words, for every 1,000 fissions, three atoms of Krypton-85 are created. The atmospheric release of krypton-85 as a result of nuclear weapon tests from 1945 to 1962 is estimated to be 5 million curies.

About 300,000 curies of Krypton-85 are produced annually by a big commercial nuclear power station, almost all of which are contained within the fuel components. This gaseous radionuclide is a byproduct of reprocessing spent nuclear fuel and is typically discharged into the atmosphere. The Three Mile Island disaster, in which numerous fuel elements broke, resulted in the discharge of about 50,000 curies of Krypton-85 into the environment.

Comparatively speaking, Mars' atmosphere contains about 1/3 as much krypton (0.3 cm3/m3). Krypton naturally occurs in a density of 0.15 µg kg-1 (µg/kg) in the Earth's crust and at a density of 0.21 g L-1 in saltwater.

During nuclear fuel reprocessing operations and as a result of earlier above-ground nuclear weapon tests, Krypton-85 was released into the environment. At the Hanford Site, the only substantial source of this particular isotope is the spent nuclear fuel that is kept in storage.

Krypton - Physical Properties

Krypton is a colourless, odourless, tasteless, radioactive gas about three times heavier than air. Sir William Ramsay and Morris Travers found it in 1898 in the residue that remained after water, oxygen, nitrogen, helium, and argon were removed from a sample of liquid air through liquefaction.

Krypton is a noble gas that is typically inert or inactive and produces a small number of chemical molecules. There are six stable isotopes of it in nature. The most common is Krypton-84, which includes approximately 57 % of natural krypton. Krypton-78, the other four stable isotopes, and their relative abundances are: Krypton-78 (0.4%), Krypton-80 (2.3%), Krypton-82 (12%), Krypton-83 (11%), and Krypton-86 (17 %).

  • Krypton has an atomic weight of Z=36 and the electronic configuration is [Ar] 3d10 4s2 4p6.
  • The element's inertness is due to this fully filled valence shell.
  • It is three times heavier than that of air.
  • It is diamagnetic in nature.
  • Krypton has an atomic mass of 83.79 u and a density of 0.003425 g cm-3.
  • Krypton is an odourless, colourless gas that has a density that is three times more than that of regular air.
  • Krypton has a face-centred cubic crystalline structure in its solid state, similar to other noble gas elements.
  • Krypton has a melting point of -157.4oC and a boiling point of -153.4oC, respectively.
  • The concentration of this inert gas is discovered to be 30% higher in the North Pole than the South Pole as a result of convective mixing in this pole. Convective mixing is the process of dispersing two groups of solid particles within one another.
  • At very high temperatures, krypton behaves like neon but glows purple rather than red.
  • When krypton is combined with other gases, it gives a greenish-yellow glow.
  • While krypton is rarely found on Earth, it is common in stars like the sun.

Krypton - Chemical Properties

The oxidation states of krypton are 0, and+2 (+2 state is specific to certain fluorine compounds alone). The element typically does not participate in reactions because of its filled outermost shell, and its oxidation state remains zero.

  • The set of isotopes that make up krypton range in mass from 69 to 102 on average. There have been identified and researched a total of 34 isotopes, of which 5 are stable isotopes that occur naturally and 1 is a radioactive isotope with a long half-life. Nature produces the isotopes 78Kr, 80Kr, 82Kr, 83Kr, 84Kr and 86Kr.
  • Krypton, which is radioactive, emits intense spectral lines that are majorly of green and yellow colour.
  • Krypton is sparingly soluble in water within the temperatures between 30° C and 40° C.
  • As Krypton is an inert gas, it is majorly unreactive. However, there is one particular reaction in which Krypton participates.
  • In its +2-oxidation state, Krypton reacts with fluorine in the presence of an electrical discharge and at an extremely low temperature of -196° C to form the product Krypton fluoride. KrF2 easily decomposes at higher temperatures. Krypton also specifically reacts with fluorine and no other halogen atoms.

Kr + F2 → KrF2

  • B(OTeF5)3 and KrF2 combine to form the unstable chemical Kr(OTeF5)2, which has a krypton-oxygen link.

Krypton - Toxicity

Krypton gas is a straightforward asphyxiant that, when inhaled in excess, can impair a person's ability to operate. Krypton functions as a narcotic and induces nausea, vomiting, and eventual loss of consciousness when inhaled in significant doses. A human can pass away in a matter of seconds in an environment that is high in krypton and low in oxygen.

Breathing an atmosphere that is 50% krypton and 50% regular air (as may occur in the vicinity of a leak) could cause individuals to experience necrosis, which is almost equivalent to breathing air at four times atmospheric pressure. 

Additionally, Krypton has the potential to bring about a number of illnesses, including cancer, thyroid gland difficulties, lung failure, kidney problems, and more. These are the explanations for why industrial facilities release the deadly krypton gas at great altitudes and far from populated areas. As a result, the gas must be handled carefully and cautiously.

Krypton has a narcotic potency seven times more than that of air. This might be harmful to anyone breathing it and is comparable to scuba diving at a depth of 30 metres (100 feet).

Krypton - Uses

  • Krypton is used alone or along with argon and neon in fluorescent lights. 
  • Additionally, it is utilised in super-fast photographic flashlights.
  • At high pressure and low temperature, it emits a characteristic bright reddish-orange colour. It is therefore used in lights at airports because the red light is visible for long distances and penetrates fog and haze to a greater extent than
  • Lasers are made using krypton fluoride, a byproduct of the interaction between Krypton and fluorine.
  • Additionally, slide projectors and tungsten-filament projector lamps employ krypton.
  • It has a number of industrial and medical applications. 
  • A krypton gas laser produces a very intense and concentrated light, Krypton and these lasers are used for medical applications such as surgery on the retina of the eye.
  • During the procedure, the powerful krypton laser light induces the blood to clot, preventing further bleeding and consequent vision loss. Additionally, the laser is so precise that no nearby tissues are harmed.
  • The krypton isotope 80Kr is used in radioactive illness diagnosis. The procedure entails ingesting the isotope in the form of nuclear medicine; to examine the scars on the lungs, the path of the medicine that was breathed was tracked using gamma cameras.
  • Another krypton isotope utilised in magnetic resonance imaging (MRI) is Krypton-83. 

Practice Problems

Q1. Which is the most abundant isotope of krypton on earth?

A. Krypton-82
B. Krypton-84
C. Krypton- 85
D. Krypton-86

Answer: The most abundant isotope of Krypton is Krypton-84, which includes approximately 57 % of natural krypton. Krypton-78, the other four stable isotopes, and their relative abundances are: Krypton-78 (0.4%), Krypton-80 (2.3%), Krypton-82 (12%), Krypton-83 (11%), and Krypton-86 (17 %).

Q2. The oxidation state of Kr in Krypton fluoride is

A. +2
B. +4
C. +5
D. +8

Answer: Fluorine being the most electronegative element is in -1 oxidation state. Krypton’s oxidation state is +2 in krypton fluoride as the formula is KrF2

So, option A) is the correct answer. 

Q3. Krypton gas when inhaled in larger quantities behaves as an

A. Carcinogen
B. Tear-inducing gas
C. Asphyxiant
D. Vision blurring gas

Answer: Krypton is thought to displace breathable air (being heavier than air), making it a non-toxic asphyxia-inducing substance. 

So, option C) is the correct answer. 

Q4. What is the significance of the emission lines of Krypton?
Answer: Ionised krypton gas discharges seem whitish due to the numerous emission lines of krypton, which makes krypton-based bulbs useful in photography as a white light source. Some photographic flashes for high-speed photography employ krypton. Mercury and krypton gas are also mixed to create illuminating signs that emit a strong greenish-blue light.

Frequently Asked Questions - FAQ

Question 1. Is detection of Krypton-85 linked with hidden nuclear power plants?
Answer: North Korea's and Pakistan's covert nuclear fuel reprocessing plants have been found using krypton-85 atmospheric measurements. These facilities were thought to be making plutonium suitable for use in weapons when they were discovered in the early 2000s. Since krypton-85 is a fission product with a medium half-life, it can escape from spent fuel when the cladding is removed. Since krypton is chemically inert and disperses widely in the atmosphere, its emission is often not harmful, although it can be detected by adequately sensitive equipment.

Question 2. Is Krypton able to glow in the dark?
Answer: When in a low pressure container krypton is placed and is exposed to an electric current, krypton shines with a smokey-white light, much like a fluorescent light bulb does. So that appears to be its glow in the dark.

Question 3. Does krypton compound occur naturally?
Answer: Krypton compounds have been created in the lab alone but are not found in nature. The artificial (artificial) chemicals are exclusively utilised for study and research purposes. Since Krypton is naturally inert it does not react under natural conditions to form any product.

Question 4. What is liquid Krypton used for?
Answer: Liquid krypton is used to build quasi-homogeneous electromagnetic calorimeters in experimental particle physics. The calorimeter of the NA48 experiment at CERN, which holds around 27 tonnes of liquid krypton, is one famous example. Since liquid argon is less expensive, this application is uncommon. Krypton has an advantage over other elements because of its smaller Molière radius (It is a constant that describes a material's electromagnetic interaction characteristics and is connected to the radiation length) of 4.7 cm, which offers superior spatial resolution and minimal overlapping.

Related Topics

S-block Elements

Alkali Metals


p-Block Elements

Calcium Oxide

Oxidation States of p-Block Elements

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