What are inorganic compounds?

Inorganic compounds are chemical substances that do not have carbon-hydrogen bonds; they are primarily composed of elements other than carbon, such as metals, non-metals, and transition elements.

In nature, inorganic compounds occur as minerals; they can even be found in a pure form. Inorganic compounds exist in less quantity and variety than organic ones.  Like organic compounds, they can be made synthetically. The study of inorganic compounds is the primary focus of inorganic chemistry.

What are the main characteristics of inorganic compounds?

The main characteristics of inorganic compounds are:

• Thermal stability: they can withstand high temperatures without decomposing or their chemical properties changing.
• Electrical conductivity: some inorganic compounds have the ability to conduct electricity, particularly ionic compounds in a molten state or in an aqueous solution. This is due to the presence of mobile ions that can carry an electric current.
• Solubility in water: the attractive forces between ions and water molecules allow ionic compounds to dissociate into ions in an aqueous solution.
• Diversity of structures: the ability of inorganic elements to form metallic, ionic, and covalent bonds gives rise to a wide range of geometries and atomic arrangements.
• Chemical reactivity: some inorganic compounds are highly reactive and can be involved in vigorous chemical reactions, while others are more stable and less reactive.
• Ability to form ionic or covalent bonds: they can form ionic or covalent bonds, which are bonds formed between a metal and a non-metal because metal atoms give up electrons to form cations, while non-metals accept electrons to form anions. Covalent bonds are formed when two non-metallic atoms share pairs of electrons.

How are inorganic compounds classified?

Inorganic compounds may be binary or ternary, depending on the number of elements of which they are composed. Within these two large classifications, they are, in turn, divided into:

Binary compounds

• Metal oxides: also called basic oxides, these are made up of a metallic element plus oxygen.
• Anhydrides: also called non-metallic oxides or acidic oxides, they are composed of a non-metallic element and oxygen.
• Peroxides: these are made up of certain metals plus binary combinations of oxygen (peroxide ion).
• Hydrides: also called metal hydrides, these are made up of a metallic element and hydrogen.
• Volatile hydrides: they are made up of hydrogen plus one of the following elements: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), carbon (C), silicon (Si), and boron (B).
• Hydracids: also known as non-metallic hydrides or hydroacidic acids, they are binary combinations between hydrogen, along with the halogens fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) — excepting astatine (At)— with the amphigenes sulfur (S), selenium (Se) and tellurium (Te) — excepting oxygen (O).
• Binary salts: the combination of two elements other than hydrogen and oxygen.
  • Neutral salts: these result from the union of a metallic and a non-metallic element.
  • Volatile salts: these result from the union of two non-metallic elements.

Ternary compounds

• Hydroxides: although their formulation and nomenclature are the same as that of the binary elements, they are ternary ionic compounds made up of a metal and an element from the hydroxy group.
• Oxyacids: these are made up of hydrogen, a non-metal, and oxygen. Sometimes, they may contain a metallic element that acts as a non-metallic one in a high oxidation state.
• Oxysalts: also known as ternary salts, these are made up of a metal, a non-metal, and oxygen.

What applications do inorganic compounds have?

Inorganic compounds have many applications in various scientific and technological fields, such as:

• Chemistry: they are used as a raw material in the production of a wide variety of products, such as fertilizers, pharmaceuticals, and cleaning products. They are also used to manufacture other raw materials; for example, sodium chloride is used in the production of chlorine and lye, which are raw materials for manufacturing plastics, paper, and cleaning products.
• Electronics: inorganic semiconductors, such as silicon, are used in the production of chips and integrated circuits. Metal oxide compounds, such as zinc oxide, are used in liquid crystal displays and light-emitting diodes (LEDs).
• Energy: inorganic compounds play an important role in energy generation and storage. They are used in rechargeable batteries like lithium batteries and in fuel cells as catalysts to facilitate the hydrogen oxidation reaction.
• Medicine and pharmacy: inorganic compounds are used in various treatments and diagnostic studies; for example, platinum compounds are used in chemotherapy; iodine compounds are contrast agents for medical imaging (such as computed tomography and magnetic resonance imaging); and iron compounds are used as nutritional supplements.
• Catalysts: they are used in the production of petrochemicals, pharmaceutical synthesis, the production of plastics, and purifying exhaust gases in the automotive industry because they act as catalysts in various chemical reactions.
• Glass and ceramics industry: thanks to their high thermal stability, inorganic compounds — such as silicon dioxide or aluminum and titanium oxides — are widely used in manufacturing glasses and ceramics, both for domestic uses and for construction and engineering.
• Textile industry: inorganic compounds are used as pigments and dyes in textile processes, but also for manufacturing paints and inks.