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The Hindenburg airship, filled with hydrogen, explodesThe Hindenburg airship, filled with hydrogen, explodesHydrogen is a colourless, odourless, tasteless, non-toxic, highly combustible gas. The most abundant element in the Universe, it forms the bulk of most stars. On Earth, most hydrogen (chemical symbol H) is joined to oxygen (O) to form water (H2O). It also occurs in organic compounds such as petroleum, ammonia and methane. Hydrogen is the simplest and lightest chemical element because each of its atoms has only two subatomic particles, one proton and one electron. Hydrogen was first discovered in 1766, when it was known as "flammable air". In 1781 it was discovered that the gas produced water when burned, for which it was given the name hydrogen (from the Greek hydro, meaning water, and genes, creator).

Bread, pasta and rice—rich in carbohydratesBread, pasta and rice—rich in carbohydrates

Hydrocarbons and carbohydrates

Hydrogen joins with carbon to form the substances known as hydrocarbons. Many of the fuel gases obtained from natural gas or crude oil, such as propane and butane, are hydrocarbons. Hydrogen also joins with carbon and oxygen to form carbohydrates. Starches in foods like potatoes and rice, and sugars in cane or beet, are rich in carbohydrates.

Hydrogen is the lightest element and the most abundant chemical substance in the Universe, making up about 75% of normal matter, and 90% of the total number of atoms.

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