Helium is a noble gas, the elements of Group 18 or 8A (Noble Gases) consist of helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Initially, these elements used to be known as inert gases because none of them could react with other elements to form compounds. It wasn’t until 1960 did scientists succeed in synthesizing the compounds of Kr and Xe. Because of this, the elements are now better known as noble gases (stable, unreactive).
As they are not reactive, in nature noble gases are found as single atoms or monoatomic. The main source of noble gases is air, except for He and Rn. Helium is found more in natural gas (at a concentration of ~1%) than in air (at a concentration of -0.00052%). Meanwhile, Rn comes from a long decay of the radioactive elements uranium (U) and decay of radium (Ra). Rn is also radioactive and has a short life so as soon as it is formed, Rn will decay into other elements.
The Discovery of Noble Gases
The discovery of noble gases that are present in limited amounts signifies the importance of accuracy in an experiment. In the past, scientists assumed that air was only comprised of N2 and O2, and also small amounts of H20 and CO2. However, around 1785, Henry Cavendish proposed the probability that there is another element in the air with a volume of around 1%.
Discovery of Helium
Many scientists overlooked this possibility and stated that the 1% was merely an error percentage in the experiment. It was not until 100 years later that William Ramsay (1852 – 1916) succeeded in identifying the other element that is now known as a noble gas, based on spectrum data. Then he tried to react the gas with other elements but failed. Because of this, the element was named argon, which means “lazy.”
Ramsay then discovered He, a gas released by radioactive minerals, by comparing the He spectrum with the Sun’s spectrum. This was because He itself had already been identified to exist in the Sun based on the analysis of the Sun’s spectrum prior to the discovery. As He and Ar did not react with other elements, Ramsay concluded that there exist monoatomic gases that are inert.
Furthermore, he was certain that these inert gases could be found in the air. For that, he conducted a distillation of liquefied air. In the end, he succeeded in discovering krypton, neon, and also xenon.
Fredrich Ernst Dorn also succeeded in discovering radon, as a decaying product of the radioactive element radium in the Earth’s crust. Ramsay then isolated this new element.
Read more about Effects of Radon on Humans
Position of Helium in the Periodic system
In the modern periodic system, elements are grouped based on the increasing atomic number and similar properties. Helium is the second element on the periodic table, It is located in group 18 or 8A and period 1 on the righthand side of the table. Helium is at the top of the periodic system, the elements below it are neon, argon, xenon, and radon.
Important Uses of Helium
Helium is used in air balloons for meteorology, transportation of wood from forests, and recreation. Helium is used to replace hydrogen gas because it is light and unreactive.
Liquid helium is used for cooling metal coils in scanner equipment, as Helium has a low boiling point.
Helium is used to replace N2 as a Heliox (He-O2) gas mixture in oxygen tanks for deep diving. This is because aside from being light and unreactive, He has a lower solubility in body tissues compared to N2. He can prevent problems when divers rise to the surface too quickly. The body has no time to release N2 in the tissues. As a result, N2 is released into the blood in the form of bubbles that can block the flow of blood thus creating great pain.
Read more about Properties of Noble Gases
Questions & Answers
Q : Is Argon a Noble Gas?
A : yes, argon is noble gas because it belongs to the element of group 8A, but argon can not yet be synthesized into compounds.
Q : Is Radon a Noble Gas?
A : yes, radon is also noble gas, radioactive elements that easily decay into other elements.