Inorganic Chemistry

I

Introduction

Inorganic Chemistry, study of the structure, properties, and reactions of the chemical elements and their compounds. Inorganic chemistry does not include the investigation of hydrocarbons—compounds composed of carbon and hydrogen that are the parent material of all other organic compounds. The study of organic compounds is called organic chemistry.

Inorganic chemists have made significant advances in understanding the minute particles that compose our world. These particles, called atoms, make up the elements, which are the building blocks of all the compounds and substances in the world around us. Just as the entire English language is constructed from combinations of the 26 letters in the alphabet, all chemical substances are made from combinations of the 112 chemical elements found on the periodic table (see Periodic Law).

Ninety elements are known to occur in nature, and 22 more have been made artificially. Elements—which include substances such as oxygen, nitrogen, and sulfur—cannot be broken into more elementary substances by ordinary chemical means. The elements are arranged in the periodic table in rows from the lightest element (hydrogen) to the heaviest (ununbium). These rows are split so that elements with similar chemical properties fall in the same columns (for more information, see the Periodic Law section of this article).

The smallest representative unit of an element is an atom (see Atom). (For example, the smallest representative of the element helium (He) is a helium atom.) When atoms that come in close contact have a sufficiently large attractive force, a chemical bond, or binding link, forms between them. The combination of two or more atoms bonded together is called a molecule. A molecule is the smallest particle of a substance possessing the specific chemical properties of that substance. For example, an atom of oxygen (O) combines with two atoms of hydrogen (H) to form a water molecule (H₂O). While molecules of H₂O possess the properties of water, individual oxygen and hydrogen atoms do not.

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Much of chemistry can be described as breaking substances apart and putting chemical components together to form new substances. This process is accomplished by breaking chemical bonds between atoms and creating new bonds, a process known as a chemical reaction.

II

Important Inorganic Compounds

Advances in inorganic chemistry have made significant contributions to modern living. For instance, synthetic fertilizers manufactured from inorganic chemicals have increased worldwide crop production. Inorganic substances used to fabricate silicon chips help power the global information age. Engineers use metal alloys in automobiles and aircraft to make them lighter and stronger. Companies also use inorganic compounds to fabricate concrete, steel, and glass—materials used to construct buildings, infrastructure, and other public works around the world.

In the United States, 10 of the 11 most commonly produced chemicals are derived from inorganic elements. These 10 inorganic chemicals (presented below in descending order of production) are used in a wide variety of applications. Sulfuric acid (H₂SO₄) is used to make fertilizers, synthetic fibers, and metals. Nitrogen (N₂) is used in recovering underground petroleum deposits, in the production of ammonia (NH₃), and as a blanketing material for shipping perishables such as fruits and vegetables. Oxygen (O₂) is used in the production of steel and plastics, in medical applications, and in rocketry. Lime (CaO) is used in the manufacture of steel and cement. Ammonia (NH3) is combined with sulfuric acid to make ammonium sulfate (NH₄SO₄), the most important of the synthetic fertilizers.

The remaining five most commonly produced inorganic chemicals (which frequently interchange rankings in production volume) are also used in a wide variety of applications. Sodium hydroxide (NaOH), commonly called lye, is used in the manufacture of paper, soap, detergents, and synthetic fibers, and is also a caustic material used as a drain cleaner. Chlorine (Cl₂) is used to manufacture vinyl chloride plastic, to disinfect drinking water, and to bleach paper during manufacturing. Phosphoric acid (H₃PO₄) is used to give soft drinks a tart flavor and to make fertilizers. Sodium carbonate (Na₂CO₃), more commonly known as soda ash, is used in the production of glass, paper, and textiles. Nitric acid (HNO₃) is used to make synthetic fibers, such as nylon; explosives, such as nitroglycerin and TNT (trinitrotoluene); and is also combined with ammonia to make fertilizer.

III

Periodic Law

Modern inorganic chemistry can be traced to the work of Russian chemist Dmitry Ivanovich Mendeleyev and German physicist Julius Lothar Meyer, who independently developed the periodic law of the chemical elements at about the same time in the late 19th century. Mendeleyev is generally credited with the findings, because he established the periodic law in 1869, and Meyer established this chemical law a year later. Both scientists, however, discovered that arranging the elements in order of increasing atomic mass produced a table of chemical properties and reactivity patterns that were regularly repeated. This phenomenon—known as the periodic law—is most often represented in the periodic table of the elements.

By arranging the elements into rows of increasing atomic mass, Mendeleyev observed that elements with similar properties fell into the same vertical columns, called groups. For example, members of the alkali metals—lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs)—are all are extremely reactive, bursting into flames when they are brought in contact with water.

IV

Structure of the Atom

Building on Mendeleyev’s work, scientists sought to explain the periodic law by understanding the structure of the atom. Through various experiments, scientists discovered that atoms consist of three types of subatomic particles—electrons, protons, and neutrons. Electrons are small, negatively charged particles that orbit a dense core in the atom called the nucleus. The nucleus is composed of the larger, positively charged protons and neutral neutrons. The attractive force between the oppositely charged electrons and protons holds the orbiting electrons around the nucleus. Ordinarily, atoms contain an equal number of protons and electrons, creating electrically neutral atoms.