Hydrogen

A hydrogen atom is the simplest element, made of just one proton and one electron. Hydrogen may be the most abundant element in the universe, but it was hard to discover. Hydrogen almost always bonds with other elements and, when it’s on its own, pure hydrogen is so light that it gets shot out of Earth’s atmosphere!

Henry Cavendish gets credit for discovering hydrogen, being the first to identify it as distinct element in a 1766 paper. He noticed the gas coming off metal shavings after pouring acid on them. He called the gas “inflammable air” because of how easily it caught fire and noted, in a later study, that the gas made water when burned. In 1783, French chemist Antoine Lavosier named the gas hydrogen, from the Greek for “water forming”. While Cavendish gets credit for the discovery, scientists had actually produced hydrogen years before. Records indicate Irish chemist Robert Boyle did so as early as 1671!

At standard temperature and pressure, hydrogen is a gas of diatomic (two atom) molecules (H₂). It is colorless, odorless, and tasteless. It’s also highly combustible and clean burning.

At extremely low temperatures (less than -253°C), hydrogen is a liquid. The liquid form is primarily used as rocket fuel. NASA has the two biggest liquid hydrogen storage tanks in the world!

At extremely low temperatures and massive pressure (like 5 million atmospheres), hydrogen is predicted to be a metallic solid. Hydrogen makes up the majority of Jupiter and other gas giant planets. The pressure is so immense in the planet’s center, that the interior likely contains metallic hydrogen!

As the most abundant element, hydrogen has a lot of uses. Great quantities of hydrogen are required to create ammonia (NH₃), which is used primarily for fertilizer and for hydrogenation, a way of processing fats and oils. Hydrogen is also used in large quantities to make methanol (CH₃OH), often used as a solvent, pesticide, or fuel. Hydrogen is also used in rocket fuel, welding, making hydrochloric acid, and purifying metallic ores. 

In nature, hydrogen fuels most stars. The atoms collide and fuse, joining together to make new elements and releasing energy in the process. Scientists are studying that process, fusion, as a possible power source and a more efficient process for nuclear power plants, which currently rely on fission (splitting atoms). 

Hydrogen fuel cells are a new and developing technology that will generate great amounts of electricity without harmful waste. Hydrogen gas is used as the fuel, releasing non-polluting water as a byproduct.

Although pure hydrogen is a gas, we find very little of it in our atmosphere. On earth, hydrogen occurs chiefly in water, but it is also present in organic matter, such as living plants, petroleum, coal, etc. It is found throughout our bodies in proteins, fats, carbs, sugars, and DNA.

Hydrogen occurs in three forms, or isotopes. Most hydrogen is in the form of hydrogen-1 or protium, having just one proton and one electron, with no neutrons in its nucleus.

Deuterium (hydrogen-2) is hydrogen’s other stable isotope. Also known as heavy hydrogen, deuterium atoms have one proton, one neutron, and one electron. Tritium (hydrogen-3) is an unstable, radioactive isotope of hydrogen. Tritium atoms have one proton, one electron, and two neutrons. Deuterium is pretty common, but tritium is exceedingly rare. While tritium can occur naturally, its primarily made as a byproduct in nuclear reactors. Both deuterium and tritium are used as fuels in nuclear fusion experiments, where just one gram of deuterium-tritium fuel makes more energy than 2,000 gallons of oil!

Unlike most elements, hydrogen was not formed in stars or supernova explosions—its nucleus, a single proton, was created during the big bang. It took nearly 400,000 years for those protons to slow down enough to bind with electrons, creating hydrogen atoms. The heavier elements formed from these original hydrogen atoms, combining in cosmic collisions to make atoms with more protons. Scientists use this same method of atomic collision to make man-made (or synthetic) elements in particle accelerators.

Hydrogen is the most abundant of all elements in the universe, accounting for about 90% of all atoms. It’s primarily found in water (H₂O) and is prepared for commercial purposes in a variety of ways. Just like Henry Cavendish, we still isolate hydrogen by treating certain metals with acid. But electricity can also separate the hydrogen and oxygen in water to capture each gas, in a process called electrolysis. In the US alone, over 3 billion cubic feet of hydrogen is produced each year!