Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds (carbon based compounds) which are the subjects of organic chemistry. The chemical behavior of the elements correlates with their position in the periodic table. The different regions of the periodic table are sometimes referred to as periodic table blocks, named according to the sub-shell in which the "last" electron resides. The s–block comprises the first two groups (alkali metals and alkaline earth metals) as well as hydrogen and helium. The p–block comprises the last six groups which are groups 3A through 8A in American group numbering and contains, among others, all of the metalloids. The d-block comprises groups 3B through 8B and contains all of the transition metals. The f–block, usually offset below the rest of the periodic table, comprises the lanthanides and actinides.
The first group of elements are named after nature of their oxides and for the basic solutions they form in water. They are soft, low melting and reactive. Group 2A elements are called alkaline earth metals because their oxides give alkaline solutions and melt at such high temperatures that they remained as solids in alchemist's fires. Magnesium which belongs to this group, in combination with other metals like aluminum is useful in varied applications like camera bodies, wheels of sports car and engine blocks. Calcium oxide(lime) is useful in many industries such as steel making, glass, paper and pesticides.
The third group contains some elements with unusual physical properties. Aluminium is the most commonly used metal, where as Gallium is used in the production of gallium arsenide semiconductors. Boron oxide is used in the production of glass. Carbon family of group 4A consists of carbon, a nonmetal followed by metalloids, silicon and germanium and then the metallic tin and lead. The first two element of group 5A are nitrogen and phosphorous. The industrial and environmental significance of their compounds is matched only by their importance in the structures and functions of bio molecules.
Oxygen and sulfur which belong to the group 6A play a very important role in the industry, environment and living things. The halogens which belong to group 7A, fluorine, chlorine, bromine and iodine react with most metals and nonmetals to form many ionic and covalent compounds. The last group 8A consists of individual atoms too 'noble' to interact with others. These are called inert gases.
Many inorganic compounds are ionic compounds, consisting of cations and anions joined by ionic bonding. Examples of salts which are ionic compounds are magnesium chloride MgCl2, which consists of magnesium cations Mg2+ and chloride anions Cl− or sodium oxide Na2O, which consists of sodium cations Na+ and oxide anions O2−. In any salt, the proportions of the ions are such that the electric charges cancel out, so that the bulk compound is electrically neutral. Important classes of inorganic salts are the oxides, the carbonates, the sulfates and the halides. Many inorganic compounds are characterized by high melting points. Inorganic salts typically are poor conductors in the solid state and are known for ease of crystallization.