Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), oganesson (Og) and radon (Rn) are the noble gases or inert gases that make up Group 18 of the periodic table. Because of their full valence shells’ (octets’) severe nonreactivity, noble gases were formerly referred to as “inert gases.” The Group 18 elements contain a full octet of eight valence electrons in their highest-energy orbitals (ns2,np6), which means that these elements have a very low propensity to gain or lose electrons to form ions or share electrons with other elements in covalent bonds. In comparison to other element groupings, the noble gases were characterized comparatively late.
They may be found in trace amounts in the atmosphere (argon accounts for around 1% of the atmosphere), while helium can be found in natural gas reserves. At room temperature, the Group 18 elements are all colorless, odorless, monatomic gases. With the exception of oganesson, all of these elements are gases at room temperature and pressure. There haven’t been enough oganesson atoms produced to know for sure, but most scientists believe it will be a liquid or solid. Radon and oganesson are both made up entirely of radioactive isotopes.
Inertness of Noble Gases
- Except when subjected to severe circumstances, noble gases are typically non-reactive. As a result, they are appropriate for use in applications to avoid undesirable responses.
- Hydrogen and helium are chemically neutral substances that do not create any bonds. Other chemicals, such as xenon, krypton, and argon, have little reactivity.
- Noble gases are indifferent to the chemical component oxygen, which imparts complete non-flammability on the noble gases.
Reactivity of noble gases follow this order: Ne < He < Ar < Kr < Xe < Rn ≪ Og
- When elements interact, their atoms’ complete their outer shells by losing, acquiring, or exchanging electrons. The fixed electronic configurations of noble gases’ atoms are the major cause of their inertness.
- This suggests that the atoms of noble gases are complete in terms of their valence shells, which are their outermost layers. They don’t exhibit any inclination to trade, acquire, or lose electrons.
- Noble gases are difficult to combine and don’t take part in chemical processes. As a result, monoatomic gases are the predominant form in which they manifest.
- In other words, they have entirely occupied their outer orbital configurations, resulting in a low energy level. As a result, inert gases are considered to have a whole electron configuration.
History of Noble Gases
- Henry Cavendish was the first to discover noble gases in the late 18th century. Cavendish distinguished these elements by removing all oxygen and nitrogen from a container of air via a chemical process.
- John William Strutt observed in 1894 that chemically derived pure nitrogen was less dense than nitrogen extracted from air samples. Based on this discovery, he inferred that another, undiscovered gas was present in the air.
- The researchers’ method varied from the Cavendish method in that they eliminated the oxygen by interacting with copper and the nitrogen by reacting with magnesium. The leftover gas was accurately identified, and the new element was dubbed “argon,” which is derived from the Greek word for “inert.”
- Helium was discovered in 1868 by Pierre Jansen, and it happens to be the solar spectrum as a brilliant yellow line with a wavelength of 587.49 nanometers. British physicist William Crookes identified the element as helium.
- Morris W. Travers and Sir William Ramsay discovered Neon, Krypton, and Xenon in 1898. Ramsay found neon by cooling a sample of air to a liquid phase, reheating the liquid, and catching the gases when they boiled out. This technique also yielded the discovery of krypton and xenon.
- Friedrich Earns Dorn discovered radon in 1900 while studying the decay chain of radium.
Occurrence of Noble Gases
- Helium is found at a concentration of around 8 ppb (parts per billion) in the Earth’s crust, making it the 71st most abundant element; it is found in a concentration of 5 ppm (part per million) (by volume) in the atmosphere. helium is the second most abundant element in the universe (23% by mass); together, hydrogen and helium account for 99% of the universe’s “normal” matter.
- Neon is found in the Earth’s crust with a concentration of 70 ppt (parts per trillion), making it the 80th most abundant element; it is present in the atmosphere at a concentration of 18 ppm (part per million) (by volume). Commercially utilized neon is extracted from liquid air via fractional distillation.
- Argon is the 56th most abundant element in the Earth’s crust, with a concentration of 1.2 ppm (from radioactive decay of potassium-40); it is present in the atmosphere at a concentration of 0.93% (by volume). To extract commercially usable argon from liquid air, fractional distillation is utilized.
- Krypton is the 81st most abundant element, with a concentration of 10 parts per trillion (ppt) in the Earth’s crust and 1 part per million (ppm) in the atmosphere. To isolate the commercially viable form of krypton from liquid air, fractional distillation is employed.
- Xenon is found in the Earth’s crust with a concentration of 2 ppt (parts per trillion), ranking it as the 83rd most prevalent element; it is present in the atmosphere in a concentration of 90 ppb (by volume). Commercially utilized xenon is extracted from liquid air via fractional distillation.
- Radon is one of the ten least abundant elements, it is only present in trace amounts in the Earth’s crust. Its atmospheric concentration is 10-9 ppt (by volume). Radon is also one of the ten least abundant elements.
Naturally Occurring Stable Isotopes of Noble Gases
Electronic Configuration of Noble Gases
|Element||Atomic Number||No. of Electrons/Shell|
|Neon (Ne)||10||2, 8|
|Argon (Ar)||18||2, 8, 8|
|Krypton (Kr)||36||2, 8, 18, 8|
|Xenon (Xe)||54||2, 8, 18, 18, 8|
|Radon (Rn)||86||2, 8, 18, 32, 18, 8|
Elemental Properties of Noble Gases
|Noble Gases||Atomic Number||Atomic Mass||Boiling Point (°C)||Melting Point (°C)||1st Ionization (E/kJ mol-1)||Density (g/dm3)||Atomic Radius|
Physical Properties of Noble Gases
- Noble gases are monoatomic, colorless, odorless, nonflammable gases with very little chemical reactivity.
- All noble gases are electrically and fluorescently conductive, which can be helpful in a number of circumstances to maintain a steady and secure atmosphere.
- All noble gases are insoluble in water.
- As you proceed from Helium to Radon in the group, the atomic radii or sizes increase. As we descend the group, there are more occupied shells, which is why this happens.
- All noble gas elements are in a gaseous form at normal atmospheric pressure and temperature. The melting and boiling values of all noble gases are incredibly low. But as we descend the group, the melting and boiling points rise as a result of the expansion of atomic size.
- All noble gas elements have low densities. However, when we continue down the group, the density will be increasing again owing to a rise in atomic size.
- The atomic size grows from Helium to Radon, which causes the attractive force to increase, increasing the polarity and decreasing the ionization potential.
- Moving from top to bottom in a periodic table group, the ionization energy decreases. These noble gases have the highest ionization enthalpy in the periodic table. This revealed that noble gases are chemically inert.
- With the exception of neon, all noble gas conducts electricity. But none of them are particularly good at conducting heat.
Chemical Properties of Noble Gases
Noble gases seldom participate in chemical processes since they are typically inert.
Noble gases are inert for the following reasons:
- Except for helium, which has ns2, all of the noble gases have fully filled electronic configurations (i.e., ns2np6) in their valence shells.
- Noble gases have extremely high ionization energies.
- The electron affinities of noble gases are exceedingly low, i.e. 0.
Applications of Noble Gases
- Helium element is also employed in the manufacture of germanium and silicon crystals.
- Helium element is employed in pipeline leak detection because of its ability to permeate through solids considerably faster than air.
- This element is also employed as a carrier gas in gas chromatography.
- Liquid helium has several applications in cryogenics, magnetic resonance imaging (MRI), and superconducting magnets due to its low melting point.
- The principal application of ultralow temperature is the formation of the superconducting state, in which the resistance to the flow of electricity is almost nil.
- Additional uses include pressurizing gas in liquid rocket propellants, helium-oxygen mixes for dives, and the working fluid in gas-cooled nuclear reactors
- The most common application of Ne is in neon signs and advertising boards. In the discharge tube, it glows reddish-orange. Additional colors are created by covering glass with various colored phosphors.
- Ne is used in indicators, television tubes, lightning arrestors, and other applications.
- It is utilized in the commercial refrigeration industry as a cryogenic refrigerant. It outperforms helium by 40 times and liquid hydrogen by three times.
- A gas laser is created by combining Ne and helium.
- In several types of gas-filled electron tubes, Ne is used solo or in mixes with other gases.
- Because helium is less soluble in blood than nitrogen at high pressure, marine divers utilize a combination of helium and Ne for breathing.
- Argon (Ar) is utilized in neon lighting tubes. When electricity is transmitted through argon, a purple-blue light is produced.
- Argon lowers chromium losses during steel production in a converter, allowing the target carbon content to be attained at a lower and lower temperature.
- Argon is also used in welding.
- Argon is also used in the production of argon lasers and argon-dye lasers. A laser is a device that emits extremely strong light of a single color (frequency).
- Because of its inertness, argon can be found in the food and beverage industries.
- It is frequently used in wine containers because it is denser than air and sits above the liquid, protecting it from oxidation and souring.
- Krypton is also known for better insulation among window panels than argon, allowing for more energy-efficient windows.
- It is utilized in the production of white lighting bulbs for cinematography. It’s been utilized to make camera flashes for high-speed photography.
- Krypton is an important component of neon-based excimer laser gas mixtures, which are employed to generate laser light for precise photolithography in semiconductor production.
- Krypton is used to make specialty flat glass for the solar, automobile, and construction industries.
- Xenon is utilized in the production of camera flashes and other types of strobe lights for usage in photography and club lighting.
- Xe lamps produce very high-quality ultraviolet rays with short wavelengths and powerful near-infrared light, both of which are essential components in the production of technologies used for night vision.
- Even though it is more expensive than other options, Xe is frequently utilized in the field of anesthesia. Additionally, it is employed as a neuroprotective and cardioprotective agent.
- The second most common cause of lung cancer, after cigarette smoking, is radon, according to reports. However, it also has useful uses for radiation, arthritic care, and bathing.
- Implantable seeds made of glass or gold that have been used in radiation to treat cancer have been manufactured using radon as a main component.
- Many auto-immune conditions, including arthritis, have been suggested to be lessened by radon exposure. For temporary pain relief, some arthritis patients have sought out small doses of radon and radioactive mine water.
Health Effects of Noble Gases
- These gases are not very hazardous, but in excessive quantities, they can be harmful. Noble gases are suffocants.
- Asphyxiant gases replace oxygen in the air, making it less available for breathing. You might pass away if you don’t have enough oxygen.
- Make sure there is adequate oxygen in the space or use a respirator mask with its own air supply before entering a room with high levels of noble gas.
- They may cause irritation to your eyes. They are not hazardous to the eyes while in gas form, but they can cause serious eye burns when in liquid form.
- They may cause irritation to your skin. They are not hazardous to the skin while in gas form, but when in liquid form, they burn swiftly yet leave the skin chilly and numb. As soon as possible, treat it as a chemical burn.
Environmental Effects of Noble Gases
- There has not been any discovery regarding effects of noble gases on environment.