Surprising and Interesting Facts About the Element Hydrogen
Hydrogen is the lightest element, with atomic number 1. It makes up about 75% of the universe’s ordinary matter by mass, according to Los Alamos National Laboratory. On Earth, it is common in compounds such as water but is rarely found as a free gas. Its small atoms, simple structure and varied chemistry make hydrogen an unusual element.
Hydrogen’s basic properties
The symbol for hydrogen is H, and its atomic weight is about 1.008 Royal Society of Chemistry. A neutral hydrogen atom has one proton and one electron. Under ordinary conditions, hydrogen occurs as a colorless, odorless gas made of molecules containing two hydrogen atoms, written H₂.
Hydrogen’s electron helps explain its chemistry. It can lose that electron to form a hydrogen ion, H⁺, or share it with another atom to form a covalent bond. The details depend on the reaction, but this capacity to form bonds accounts for hydrogen’s presence in many familiar compounds.
Hydrogen has three naturally occurring isotopes: protium, deuterium and tritium Royal Society of Chemistry. Isotopes of an element have the same number of protons but different numbers of neutrons. Protium, by far the most common isotope, has no neutrons. Deuterium has one, and tritium has two. Tritium is radioactive and occurs in nature in very small amounts.
Common in space, bound on Earth
Hydrogen accounts for about 90% of the atoms in the universe, according to Jefferson Lab. It is the main fuel in stars, where nuclear fusion converts hydrogen into helium and releases energy. The Sun, like other stars, contains a large amount of hydrogen.
Earth is different. Here, hydrogen is mostly bound to other elements. Water is H₂O, and hydrogen is also part of many organic compounds. As a result, the element can be abundant in the materials around us without being readily available as hydrogen gas. Producing usable hydrogen generally means separating it from a compound.
How hydrogen is produced
Two common industrial routes are steam reforming, which uses natural gas and steam, and electrolysis, which uses electricity to split water Los Alamos National Laboratory. The emissions associated with hydrogen production depend on the process and its energy sources. Electrolysis, for example, does not by itself determine whether the hydrogen is low-emission; that also depends on how the electricity is generated.
A straightforward example is water electrolysis. Water molecules contain two hydrogen atoms and one oxygen atom. When an electric current passes through water in an electrolyser, the process separates the hydrogen and oxygen into gases. The hydrogen comes from the water; the electricity supplies energy for the separation.
That example also clarifies a common misconception about hydrogen as a fuel. Hydrogen is an energy carrier, not a primary source of energy. Energy must be used to produce it. When hydrogen reacts with oxygen, it releases energy and forms water, but the amount and source of energy used to make the hydrogen matter when assessing the full process.
Where hydrogen is used
Hydrogen is used in the production of ammonia, which is an important ingredient in many fertilizers Los Alamos National Laboratory. It is also used in food processing. In hydrogenation, hydrogen reacts with some oils, changing their chemical structure and helping make them more solid Royal Society of Chemistry.
Hydrogen can also be used as a fuel. When it reacts with oxygen, water is the main product of the reaction. That does not mean every use of hydrogen has no emissions: production, storage and delivery all affect its environmental impact.
Liquid hydrogen has a role in rocket propulsion. It must be kept at very low temperatures to remain liquid, so storage and handling require specialized equipment. NASA describes hydrogen’s use in rocket propulsion.
Why hydrogen’s place on the periodic table is unusual
Hydrogen is often placed above the alkali metals in periodic tables because it has one electron. Like those metals, it can lose that electron in some reactions. But hydrogen is a nonmetal at ordinary conditions and commonly shares electrons in covalent bonds. It differs enough from the elements around it that some periodic tables show it separately Los Alamos National Laboratory.
Hydrogen also differs sharply from helium, the next element on the periodic table. Helium has two electrons in its only electron shell and is chemically inert under ordinary conditions. Hydrogen has one electron and readily forms compounds. Their position next to each other reflects their atomic numbers, not similar chemical behavior.
Discovery and name
Henry Cavendish is credited with identifying hydrogen as a distinct gas in 1766. He studied the gas released when certain metals reacted with acids Los Alamos National Laboratory. The name hydrogen comes from Greek roots associated with water formation. The name refers to the fact that hydrogen reacts with oxygen to produce water Royal Society of Chemistry.
Key Takeaways
- Hydrogen is the lightest element, with atomic number 1 and an atomic weight of about 1.008.
- It makes up about 75% of the universe’s ordinary matter by mass and about 90% of its atoms.
- On Earth, hydrogen is usually part of compounds such as water. It must be separated from those compounds to produce hydrogen gas.
- Hydrogen has three naturally occurring isotopes: protium, deuterium and trace amounts of radioactive tritium.
- Water electrolysis is one way to produce hydrogen. Its environmental impact depends in part on the source of the electricity.
- Hydrogen is used in ammonia production, food processing and rocket propulsion.
