We explain what noble gases are, when they were discovered and how they are classified. We also explain what their characteristics and properties are.
What are noble gases?
They are known as noble gases or inert gases. set of chemical elements that make up group 18 (VIIIA) of the Periodic Table of elements and which have a series of characteristics in common: the most important is their very low degree of reactivity, that is, their low capacity to form compounds and structure complex molecules. There are only a few compounds with these elements.
Noble gases, under normal temperature and pressure conditions, are gases monatomic devoid of color, smell and tastewhich are present in varying proportions in the air of the atmosphere and in other situations in nature.
Despite its low reactivity, or precisely as a consequence of itNoble gases have various applications in human industries and are mass produced.
See also: Ideal gases
History of noble gases
Most of these chemical elements They were discovered around the 19th centurywhen Pierre Janssen and Joseph Norman Lockyer, examining the sun, discovered helium, whose name comes from the Greek word for the king star.
Krypton, neon and argon were later discovered. from the chemical study of air and, towards the end of the 19th century, Lord Rayleigh and William Ramsay postulated the existence of noble gases, which earned them the Nobel Prize in Physics and Chemistry.
It was not until the 20th century that its industrial production began on a large scale, as more of its particularities and uses were discovered.
Examples of noble gases
There are seven noble gases:
- Helium (He). It is the second most abundant element in the universe, produced by nuclear reactions in the hearts of stars through the fusion of hydrogen. It is very popular because it alters the human voice when inhaled and because it is much lighter than air, so it always tends to rise.
- Neon (Ne). Very abundant in the universe, it is what gives the red tone to the light from fluorescent lamps. It is used in tube lighting (neon) and in TV technology.
- Argon (Ar)Common in atmospheric air, it is an element widely used as an insulator in industry and in obtaining different lasers.
- Krypton (Kr). Despite being a noble gas, it is known to react with fluorine and a few other elements that possess strong electronegativity. It emits very bright green and orange light. It has six stable isotopes and seventeen radioactive ones.
- Xenon (Xe)It is a very heavy gas, present on the Earth’s surface only in trace amounts. It was the first noble gas to be synthesized.
- Radon (Rn). It arises from the decay of radioactive elements such as radium-226 or actinium (then it is called actinon), making it a noble but radioactive gas, whose most stable isotope (222Rn) has a half-life of 3.8 days and It then decays into polonium-218.
- Oganesson (Og). Also called eka-radon, Ununoctium (Uuo) or element 118, it is a synthetic and highly radioactive element. The results of their discovery were finally published in 2006.
Why are they called noble gases?
Initially, upon discovery, these elements They were called inert gases or rare gases.as they were thought to be chemically passive and rare in the universe.
Both ideas turned out to be false, so The use of “noble gases” is preferredtranslation of the German term with which Hugo Erdmann baptized them in 1898: Edelgas.
this name comes on loan from “noble metals” such as goldwhose chemical behavior also shows a tendency towards low reactivity, that is, not forming chemical compounds.
Noble gases or inert gases?
The term inert gases is generally used as synonym for noble gasesalthough the latter term is preferred.
This is because there are others gases that, under certain circumstances, can behave inertlywithout being part of the noble gases: such is the case of nitrogen, whose reactivity increases only at high temperatures, for example.
Electronic configuration of noble gases
The reason why the noble gases are little reactive can be explained by their electronic configuration, since its outermost shell or valence shell is always completewithout having to accept or give up electrons.
This means that, with a few exceptions, noble gases do not participate in chemical reactions to form chemical compounds, since on their own they are very stable.
Reactivity of noble gases
The noble gases They are not very reactive, that is, they practically do not form chemical compounds.. This means that they do not react much with other substances, they do not even react between atoms of the same gas, as occurs with diatomic gases such as oxygen (O2) or hydrogen (H2), which form molecules. Helium and neon are particularly inert and are followed by argon, krypton, xenon and radon.
The exceptions to this rule are fewand generally involve heavier noble gases, such as xenon or radon, capable of forming compounds with fluorine and oxygen, such as krypton hexafluoride (KrF6) or xenic acid (H2XeO4).
Under particular temperature conditions (-60 and -90 °C respectively), krypton can bind with nitrogen and oxygen stably. No neon compound has been identified in the universe to date.
Uses of noble gases
Noble gases have numerous uses for humans and One of the main ones is to act as insulators.since their low reactivity allows them to do so.
Besides, They are usually liquefied to use them as refrigerantsvital for delicate machinery such as superconducting magnets used in nuclear magnetic resonance imaging. They are also used in cryogenic processes.
On the other hand, Helium is used in a mixture with other gases as a respirable componentfor astronauts and divers, since it reduces the narcotic effect of “deep sea sickness,” which can kill a diver if he rises from the deep sea too quickly.
Another use of helium is as gas for inflatable balloons or dirigiblesreplacing hydrogen which is highly flammable.
A very common use of neon, xenon and krypton is in lightingsince they are used to refill incandescent bulbs and produce specific colors of light, in addition to extending the life of the lamp.
They are also used for the laser production used in surgery or industrial procedures.
Physical properties of noble gases
The noble gases are almost always gases, although can be liquefied and then solidified, under specific conditions of pressure and temperature. Since they have very weak intermolecular forces, they have low melting and boiling points, all more or less in the same range.
Helium is particular: it is the element with the lowest known melting and boiling point and the only element that is superfluid. Besides, Helium cannot be solidified through low temperaturesbut under peculiar pressure conditions.
On the other hand, all noble gases have stable isotopes except radon, which is radioactive and after 3.8 days its most stable isotope (radon-222) decays into polonium-218.
Abundance of noble gases
Noble gases are more abundant in the universe as their atomic number decreasesThe lighter they are, like helium, the more abundant they are; in fact, the amount of helium in the universe increases as atomic fusion of hydrogen from stars takes place.
Neon, argon, xenon and krypton are in the very air we breathe, from where they can be separated by liquefaction and fractional distillation; while radon, rarer, appears during the decay sequences of radium and other radioactive materials.
Danger of noble gases
The noble gases They are not toxic or dangerous in themselves But they pose a mechanical danger to living beings: they are potential asphyxiating gases, since they displace oxygen in the air we breathe.
Thus, an individual locked in a room in which noble gases are injected can faint and then die of asphyxiation due to lack of oxygen in the air.
Furthermore there are intrinsic dangers of radioactive noble gasessuch as radon, oganesson and some isotopes of krypton, which are highly carcinogenic.
May be useful to you: Alkali metals