Ammonia

Ammonia is an inorganic chemical compound made of nitrogen and hydrogen. It has the chemical formula NH3. This substance is a colorless gas with a very sharp, pungent smell.

It is a stable binary hydride and is the simplest pnictogen hydride. Ammonia is highly significant because it serves as a fundamental building block for many other chemicals. It is also a vital part of the global food system. About 70% of all industrially produced ammonia is used to create fertilizers. These fertilizers help provide the nutrients that terrestrial organisms need to grow.

To understand how an ammonia molecule is built, we can look at its shape. The molecule has a trigonal pyramidal shape. This shape is predicted by the valence shell electron pair repulsion theory, often called VSEPR theory.

In this structure, a central nitrogen atom is bonded to three hydrogen atoms. The nitrogen atom has five outer electrons. When it bonds with the three hydrogens, it uses three electrons for the bonds. This leaves one lone pair of electrons. This lone pair repels the bond pairs more strongly than they repel each other. Because of this extra repulsion, the bond angle is 106.7 degrees rather than the standard 109.5 degrees found in a regular tetrahedron. This specific shape gives the molecule a dipole moment and makes it polar.

Ammonia can exist in several different physical states depending on its environment. As a gas, it is lighter than air, with a density only 0.589 times that of air. It can be easily liquefied because of strong hydrogen bonding between its molecules. In its liquid form, ammonia is a powerful ionizing solvent.

This means it can dissolve many different substances. For example, liquid ammonia can dissolve alkali metals. This process creates highly colored, electrically conductive solutions. These solutions contain solvated electrons, which are free electrons surrounded by a cage of ammonia molecules. At low concentrations, these solutions appear deep blue. At higher concentrations, they look metallic and can conduct electricity.

There are several ways ammonia is produced and moved around the world. In nature, ammonia is created through a process called nitrogen fixation. However, humans produce much more ammonia through an industrial method known as the Haber process. This discovery revolutionized agriculture by providing a way to make cheap fertilizers.

In 2021, the global industrial production of ammonia reached 235 million tonnes. To move this massive amount of material, companies use various transportation methods. They use tankers on roads, tank wagons on rails, and gas carriers on the sea.

They also use pressurized cylinders for smaller amounts.

The history of the name "ammonia" is tied to ancient times and religious sites. The name is derived from the Egyptian deity Amun. In Greek, this deity was called Ammon.

Near the temples of these gods, priests and travelers would burn soil that was rich in ammonium chloride. This soil came from animal dung and urine. The Roman writer Pliny also mentioned a salt called hammoniacum in his work, Natural History. He noted its proximity to the Temple of Jupiter Amun in Cyrenaica. While some believe this was actually common sea salt, the name for these compounds remained tied to the ancient god.

Ammonia is also a fascinating subject in the study of space and astronomy. It is not just found on Earth; it is present throughout the Solar System. Scientists have detected it on Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

On smaller, icy bodies like Pluto, ammonia plays a very important geological role. It can act as an antifreeze. When ammonia mixes with water, the resulting mixture has a much lower melting point. This allows icy worlds to potentially retain internal oceans and stay geologically active even at extremely low temperatures.

Finally, we must consider how ammonia interacts with the atmosphere and living things. In the atmosphere, ammonia comes from natural sources and human activities like agriculture. About 80% of atmospheric ammonia comes from agriculture, including fertilizers and livestock manure.

Ammonia can also react with sulfuric and nitric acids to form sulfate-nitrate aerosols. These aerosols can impact both the climate and human health. Inside living animals, ammonia is a common nitrogenous waste. Because it is toxic and can damage cells and tissues, most animals must excrete it. They typically do this through urine, often by converting it into a substance called urea first.