Science Geek
Helium (Element 2: He)
Helium is the second element on the periodic table and belongs to the noble gas family. With two protons and two electrons, its electron configuration (1s²) gives it a completely filled outer shell, rendering it almost chemically inert. It is colorless, tasteless, odorless, non-toxic, and exists as a monatomic gas under standard conditions (Britannica).
The element was first identified in the Sun’s corona by French astronomer Pierre Janssen during a solar eclipse in 1868, when he detected an unexplained yellow spectral line. Independently, Norman Lockyer named this unknown element “helium” from the Greek word helios (“Sun”) that same year. On Earth, helium was isolated by Sir William Ramsay in 1895 through experiments with the mineral cleveite, assisted by Swedish chemists Per Teodor Cleve and Nils Langlet, confirming the solar discovery in terrestrial samples (Lanl).
Helium’s physical behavior is extraordinary. It has the lowest boiling point (4.222 K or −268.93 °C) and cannot be solidified at normal atmospheric pressure – remaining liquid even near absolute zero unless under high pressure. Its liquid form (helium II) exhibits superfluidity: zero viscosity and extreme thermal conductivity, properties important to low‑temperature physics and quantum fluid research (AllAboutChemistry).
Helium is commercially extracted almost exclusively from natural gas reservoirs, especially in the United States, where concentrations may reach 7%, using fractional distillation to purify it to >99.99%. On Earth it occurs only at about 5 ppm in air because its lightness allows it to escape the atmosphere over time.
Common uses of helium span a wide range: as a lifting gas in balloons, airships and meteoric balloons where hydrogen would pose a fire hazard; as a cooling agent in liquid form for superconducting magnets in MRI and research facilities; as a protective gas for arc welding or semiconductor manufacturing; and clinically in breathing mixtures (e.g. heliox) to reduce nitrogen narcosis during deep-sea dives.
Physical Data at a Glance
| Property | Value |
|---|---|
| Atomic weight | ~4.0026 amu (Material‑Properties) |
| Density (gas, STP) | ~0.0001786 g/cm³ (0.1786 g/L) (Lenntech) |
| Atomic radius (covalent) | ~28 pm (Lenntech) |
Isotopes of Helium
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Helium‑4 (⁴He): By far the most abundant and stable isotope (~99.9998%) on Earth, produced in stars and via alpha decay.
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Helium‑3 (³He): Rare and stable (~0.00014%), of interest in cryogenics and potential future fusion energy research (Wikipedia).
Safety Notes
While helium is chemically inert and non‑flammable, it presents specific safety concerns:
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Asphyxiation risk: In enclosed spaces, helium displaces oxygen and can lead to suffocation.
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Cryogenic frostbite: Liquid helium is extremely cold (near absolute zero) and can cause severe cold burns on skin or eyes.
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No flammability risk: Unlike hydrogen, helium is safe around ignition sources, but still requires careful handling when stored as liquid or in high-pressure cylinders.
Further Exploration
This video explores helium’s discovery, unique properties, and everyday uses – from floating balloons to ultra-cold superfluidity – in an accessible and informative format.
