Quick answerHelium (He) is a noble gas with atomic number 2 and an atomic mass of 4.0026 (2023), in group 18, period 1. It was discovered by Pierre Janssen and Norman Lockyer in 1868. It is used for cooling MRI scanners and cryogenics for particle accelerators. Its electron configuration is 1s2.
Helium is the gas that lifts balloons and makes voices squeaky, but its most serious job is keeping things colder than almost anything else on Earth. Liquid helium cools MRI scanners and particle accelerators to near absolute zero, and it is also the safe, non-flammable lifting gas for airships and balloons. It is the only element that never freezes, even at the coldest temperatures ever reached.
Key facts
| Symbol | He |
|---|---|
| Atomic number | 2 |
| Atomic mass | 4.0026 (IUPAC standard atomic weight, 2023) |
| Category | noble gas |
| Group | 18 |
| Period | 1 |
| Block | s-block |
| Electron configuration | 1s2 |
| Discovered | Pierre Janssen and Norman Lockyer, 1868 |
| Uses | cooling MRI scanners, cryogenics for particle accelerators, lifting gas for balloons and airships, pressurising rocket fuel tanks, leak detection |
Overview
Helium is a colourless, odourless noble gas with atomic number 2 and an atomic mass of 4.0026, the second-lightest element after hydrogen. It was first spotted in the Sun's spectrum during a solar eclipse in 1868 by Pierre Janssen and Norman Lockyer, who named it after Helios, the Greek sun god, before it was found on Earth. Its electron configuration is 1s2, a full shell that makes it almost completely unreactive: helium forms no stable compounds under normal conditions and simply will not burn. That safety is why it replaced flammable hydrogen as the lifting gas for balloons and airships. Helium's most important job, though, is cold. Liquid helium boils at a temperature closer to absolute zero than any other substance, and it is the only element that never freezes, even at the coldest temperatures ever reached. It cools the superconducting magnets inside MRI scanners and particle accelerators, and it pressurises rocket fuel tanks and helps detect leaks in sealed systems. Helium is rare on Earth because it is so light that it escapes into space; most of it is extracted from natural gas, where it has built up from the decay of radioactive elements underground.
Frequently asked questions
What is helium used for?
Helium is mainly used as a coolant: liquid helium keeps MRI scanners and particle accelerators near absolute zero. It is also the safe, non-flammable lifting gas for balloons and airships, it pressurises rocket fuel tanks, and it is used to detect leaks. Smaller amounts go into lasers, diving gas mixtures and welding.
What is the symbol for helium?
The chemical symbol for helium is He, from its name, which comes from Helios, the Greek sun god. It was first spotted in the Sun's spectrum in 1868 before being found on Earth. Helium has atomic number 2 and an atomic mass of 4.0026, making it the second-lightest element after hydrogen.
What is the atomic number of helium?
Helium has atomic number 2, so it is the second element in the periodic table. Its atom holds two protons and two electrons, and its standard atomic mass is 4.0026. It is a noble gas in group 18 and period 1, with the electron configuration 1s2, a full shell that makes it almost completely unreactive.
Why does helium make your voice squeaky?
Helium makes your voice squeaky because sound travels much faster through light helium gas than through air. Your vocal cords still vibrate at the same rate, but the sound waves resonate at higher frequencies in helium, so your voice sounds higher pitched. Breathing helium is not safe, though, as it can deprive you of oxygen.
Is helium flammable?
No, helium is not flammable. It is a noble gas with a full outer electron shell, so it does not react with anything under normal conditions and cannot burn. That is why it replaced hydrogen, which is highly flammable, as the lifting gas for balloons and airships after early airship disasters.
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Keep exploring
- Periodic table — all 118 elements
- Neon (Ne) — another noble gas, atomic number 10
- Argon (Ar) — another noble gas, atomic number 18
- Krypton (Kr) — another noble gas, atomic number 36
- Xenon (Xe) — another noble gas, atomic number 54
- Radon (Rn) — another noble gas, atomic number 86
- Oganesson (Og) — another noble gas, atomic number 118
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.