Helium, with the chemical symbol He and atomic number 2, is a colorless, odorless, tasteless, non-toxic, inert gas. It is the second lightest element in the periodic table, after hydrogen. Helium is the second most abundant element in the universe, after hydrogen, and is primarily produced through the nuclear fusion of hydrogen in stars.

In terms of ranking, helium is a highly valuable and versatile element with a wide range of applications. One of the most well-known uses of helium is in balloons, where its low density and non-flammable properties make it ideal for lifting objects. Helium is also used in cryogenics, as it has a very low boiling point and is used to cool superconducting magnets in MRI machines and particle accelerators.

In the industrial sector, helium is used in welding, as it provides an inert atmosphere that prevents oxidation and improves the quality of the weld. Helium is also used in leak detection, as its small atomic size allows it to escape from even the smallest of leaks. In the aerospace industry, helium is used to pressurize and purge fuel tanks, as well as in rocket propulsion systems.

In the medical field, helium is used in a variety of applications, including as a coolant for MRI machines and as a carrier gas for respiratory therapies. Helium is also used in the production of semiconductors, where its inert properties prevent contamination of the materials being processed.

Overall, helium is a highly valuable and versatile element with a wide range of applications across various industries. Its unique properties make it an essential element for a wide range of technologies and processes. As such, helium is consistently ranked as one of the most important elements in the periodic table, both in terms of its abundance in the universe and its practical applications here on Earth.