About

• Helium is a colourless, odourless gas that is unreactive. It is the lightest noble gas.
• Helium is named after the Greek word for the sun, helios, as it was first identified in the sun’s corona (the sun is composed of 25% helium).
• It is the second most abundant element in the universe. It is present in all stars.
• On the Earth, most helium is a radioactive decay product of uranium and thorium. It is found under the Earth’s crust with other natural gases. 
• The gas is non-toxic, but cannot be breathed on its own, because it displaces the oxygen humans need for respiration.

Uses

• Helium is often used to fill decorative balloons, weather balloons and airships because of its low density. 
• As it is very unreactive, helium is used to provide an inert protective atmosphere for making fibre optics and semiconductors, and for arc welding. 
• Helium is also used to detect leaks, such as in car air-conditioning systems.
• A mixture of 80% helium and 20% oxygen is used as an artificial atmosphere for deep-sea divers and others working under pressurised conditions.
• Helium’s cooling properties are indispensable to scientific research and medical diagnostic equipment including magnetic resonance imaging (MRI) machines, NMR spectrometers and even the Large Hadron Collider. 
• Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. 
• Helium is used to cool nuclear reactors.