Helium, with the chemical symbol He and an atomic number of 2, is a noble gas in Group 18 of the periodic table. The lightest of the noble gases, helium is the second most abundant element in the universe and plays a significant role in various fields, such as energy production, medicine, space technology, and industrial applications. Although helium was first discovered in the Sun, it was later found on Earth, leading to significant scientific and industrial advancements.

Discovery and Historical Development of Helium

Helium was first observed in 1868 by French astronomer Pierre Janssen during a solar eclipse in India. Using a spectroscope to study the Sun's chromosphere, Janssen noticed a new yellow spectral line in a solar prominence (a gas eruption in the Sun's atmosphere). He predicted that this line signified the presence of an element that had never been discovered on Earth. This spectral line was independently observed by English astronomer Joseph Norman Lockyer, and it was understood that it did not originate from any known element on Earth. Lockyer and English chemist Edward Frankland named this new element helium, derived from the Greek word helios, meaning "sun."

Helium, discovered in the Sun, was first isolated on Earth in 1895 by Scottish chemist Sir William Ramsay from a mineral called cleveite, which contained uranium. This discovery earned Ramsay the Nobel Prize in Chemistry in 1904. Furthermore, his work helped establish the noble gases group in the periodic table.

Chemical Properties of Helium

Helium is a colorless, odorless, and tasteless gas, lacking properties like color, smell, or taste. It exists as a gas at room temperature and has low density and a very low boiling point (−268.93°C). Helium belongs to the group of rare gases (noble gases) and is chemically inert (non-reactive). This means it is generally found in its free state in nature.

The nucleus of a helium atom contains only two protons, which is why its atomic number is 2. It also has two electrons, with an electron configuration of 1s². Due to these properties, helium does not form chemical bonds and typically does not react with other elements. A key characteristic of noble gases is that their outer electron shells are filled, which results in extremely low chemical reactivity.

Uses of Helium

In addition to its chemical stability, helium is widely used in many industrial and scientific applications due to its physical properties. Some of its primary uses include:

1. Space Technology and Airships Helium is a much safer gas than hydrogen, as hydrogen is flammable and explosive, whereas helium is completely non-flammable. Therefore, helium is preferred over hydrogen for airships and balloons. Additionally, in space research, helium is used in rocket fuel systems for cooling purposes.
2. Medical Applications Helium is commonly used in magnetic resonance imaging (MRI) machines. MRI machines use powerful magnetic fields to create images of organs and tissues inside the body, and helium is required to cool these magnetic fields. Its low boiling point makes it highly efficient for this cooling process.
3. Laser Technology Helium is used in certain lasers, such as the Helium-Neon (HeNe) laser. These lasers are used in scientific research and industrial applications that require high precision.
4. Industrial Applications Helium is also used in industrial applications like air balloons, ship and aircraft cooling systems, and high-tech applications such as dark matter research and superconductors.
5. Cooling and Cryogenic Applications Helium is widely used to cool superconducting materials. This process is critical in scientific research and technological devices.

Helium's journey began with its discovery in the Sun, followed by its isolation on Earth and eventual industrial use. With its chemical inertness, low density, and non-flammable properties, helium has become an indispensable element in many fields, particularly in space technology, medical applications, and industrial cooling. Its contribution to scientific and technological advancements continues to be significant, and helium will play a crucial role in future developments.