Hydrogen — Overview & Properties

The Hydrogen Element

Hydrogen ($H$) is an element found on the top left of the periodic table. It is the first element of the table having an atomic number of 1. $H$ is the most abundant element in the universe. The most common isotope of $H$ has one proton, one electron, and no neutrons. Its isotope notation is written as $^1 H$.

Discovery of Hydrogen

Hydrogen can exist as a diatomic gas, $H_2$. $H_2$ has no color, odor, or taste. It is also non-toxic, but it is highly combustible or flammable. In the 1700s, Henry Cavendish reacted metallic compounds with acid to generate a gaseous substance that when burned formed water. This gaseous compound was later discovered to be $H_2$. When the acid reacted with a metal, $H_2$ gas is formed, which is flammable. When $H_2$ burns, it reacts with oxygen in the air to form water, $H_2O$.

Later in the 1700s, after the discovery of $H_2$ it was first used to lift a balloon. Hydrogen gas is lighter than air so it will lift balloons, much like common helium balloons today. In the 1800s, the first air travel balloons or airships were created and hydrogen gas was used to lift these ships. In 1937, an event that would become known as the "Hindenburg disaster" where a Hindenburg class airship caught on fire. The exact cause of the fire is unknown, but the use of flammable hydrogen gas helped to fuel the fire. This led to the decline of airships. Today balloons for parties use the safer and inert, helium gas.

Hydrogen Compounds

There are many compounds that contain hydrogen. Hydrogen is often found on Earth in water molecules or organic compounds. $H$ can readily form bonds with non-metallic compounds like itself. When $H$ is oxidized (loses electron) $H^+$ is formed. $H^+$ has no electrons and one proton, therefore it is often referred to as a proton.

There are different types of compounds containing hydrogen, some examples include:

• Acids: these compounds contain an anionic species paired with hydrogen. Acids are considered proton donors and will lose the $H^+$ species. Strong acids break apart into an anion and $H^+$ in water. The hydrogen ion reacts with water to generate hydronium ($H_3O^+$).

• Hydrides: these compounds form when hydrogen forms a bond with a less electronegative atom. This causes $H$ to take on a partial negative charge. Often this occurs with metal and metalloid atoms.

• Organic compounds: organic compounds contain carbon atoms, where carbon forms four bonds with other atoms. $H$ is bonded to carbon where it does not form a bond with another atom. Hydrocarbon compounds are compounds with only carbon and hydrogen atoms.

Isotopes of Hydrogen

Isotopes occur when an atom gains or loses neutrons. Hydrogen has three well-known isotopes. The most abundant hydrogen isotope is protium, $^1H$. Protium has one proton and no neutrons. Deuterium, $^2H$ contains two neutrons. In water molecules where the hydrogen is replaced with deuterium, it is known as heavy water. Heavy water is used in nuclear reactors to absorb neutrons. Solvents with hydrogen replaced with deuterium are known as deuterated solvents. They are commonly used as a labeling solvent in NMR spectroscopy. Tritium, $^3H$, contains three neutrons and is a radioactive isotope of hydrogen.

(Video) Properties of Hydrogen | Environmental Chemistry | Chemistry | FuseSchool

by FuseSchool - Global Education

This video will teach you about some of the important properties of hydrogen that allow it to be used in so many molecules around us.

Do be aware that there is a "scientific jump scare" at the 2:40 mark. This loud sound happens when hydrogen is heated up and reacts with oxygen in the air.

Hydrogen: Important Characteristics of Hydrogen