Properties and Overview of Helium

Overview:

Helium (He) is a colorless, odorless, tasteless, and non-toxic gas with the chemical symbol He and atomic number 2. Following hydrogen, it is the second lightest and most abundant element in the universe. Helium was first discovered in the solar spectrum in 1868 by astronomer Jules Janssen and independently by Norman Lockyer, who noticed a yellow spectral line during a solar eclipse. This element is unique in that it was discovered in space before being found on Earth, where it was later identified in natural gas by chemists William Ramsay, Per Teodor Cleve, and Nils Langlet. Physically, helium exists as a gas under standard conditions, but it can be liquefied at extremely low temperatures. It is notable for having the lowest boiling point of any element, at approximately -268.93°C and its melting point occurs only under extreme pressure. Helium does not solidify under normal atmospheric pressure, remaining a liquid even near absolute zero. The density of helium gas at room temperature is about 0.1786 grams per liter, making it much lighter than air. Helium is also the only element that cannot be frozen solid by cooling alone; it requires low temperature and high pressure to solidify.
Chemically, helium is exceptionally inert, falling into the category of noble gases. Its inertness is due to its complete electron shell, which consists of just two electrons, making it highly stable and unlikely to form chemical bonds under normal conditions. Helium does not react with other elements or compounds, even under extreme conditions, and thus, it is rarely found in chemical compounds. This chemical inertness makes helium valuable in environments where reactions with other materials must be avoided, such as in controlled atmospheres for manufacturing processes.
Regarding safety, helium is considered non-toxic and generally safe for use in most applications. However, there are safety concerns associated with the inhalation of helium. While inhaling helium can cause a temporary high-pitched voice by displacing air in the lungs, doing so in excessive amounts can lead to asphyxiation due to a lack of oxygen. This is because helium does not support respiration and can displace oxygen in confined spaces, leading to unconsciousness or death in extreme cases. Additionally, care must be taken when handling liquid helium, as its extremely low temperatures can cause severe frostbite or cold burns upon contact with skin.

Production:

The production of helium primarily involves the extraction from natural gas reserves, where it is found in small concentrations, typically up to 7% by volume. Helium is a byproduct of the radioactive decay of heavy elements such as uranium and thorium, which release alpha particles that capture electrons and form helium atoms. The extraction process includes cooling the natural gas to extremely low temperatures to liquefy other gases like nitrogen and methane, leaving helium in its gaseous state for separation. The United States has been the leading producer of helium, particularly from fields in Texas, Wyoming, and Kansas, though other countries like Qatar and Algeria have also become significant producers.

Applications:

Helium has a wide range of applications due to its unique physical and chemical properties. One of its most well-known uses is in lighter-than-air balloons and airships, whose low density allows them to float. In scientific research, helium is essential for cryogenics, particularly in cooling superconducting magnets in MRI (magnetic resonance imaging) machines and particle accelerators because of its extremely low boiling point. Liquid helium is the coldest substance available, making it indispensable for experiments requiring ultra-low temperatures. Helium is also used as a protective inert gas in welding and in the production of semiconductor devices, where it prevents unwanted chemical reactions.

Summary:

Helium is an essential and versatile element with properties that make it valuable in various fields, from scientific research to industrial applications. Its inertness, low boiling point, and low density are vital attributes that enable its use in environments where chemical reactions must be minimized and in applications requiring ultra-low temperatures. Helium production, primarily from natural gas, has made it a critical resource in medical and technological sectors. While generally safe, handling helium, particularly in its liquid form or confined spaces, requires caution to prevent potential hazards.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for helium below: