Element Definition Chemistry
Chemical element is the substance that cannot be decomposed into simpler substances by the common chemical processes in chemistry or chemical science. All the periodic table elements are distributed throughout the entire universe and their isotopic compositions have been estimated by a wide range of chemical and spectroscopic studies on the sun and solar systems like stars, galaxies, nebulae, and interstellar space. Element is the fundamental chemical materials of matter or chemical compound now extends up to 112, with the scopes for further addition.
In this article, we study the origins, abundance, and chemical behavior or facts of the periodic table element. Only 75 elements occur in the earth’s crust in a concentration greater than 10-4 ppm. The average relative content of an element in any natural system is called its abundance. Spectroscopic analysis of the celestial bodies and analysis of materials provided knowledge about the abundance of elements over the whole universe or cosmos (cosmic abundance). The abundance of the elements on the earth is somewhat different from cosmic abundance. Each abundance data (earth, atmosphere, and surface water) is helpful in providing systematic scientific information of a chemical element with respect to their formation, properties, stability, and occurrence.
Origins of Chemical Element in Periodic Table
A very small fraction of the mass of the earth crust (hydrosphere and atmosphere) is available for direct analysis and study of composition, facts, and chemical properties of an element. Systematic data and other studies primarily describe that the earth consists of several zones bases on the density of the naturally occurring chemical elements. The several types of earth zones consist, the crust (∼36 kilometers in the depth of earth), the mantle (36 to 2900 kilometer), and the core (2900 kilometers to the center of the earth). Primarily the crust describes a heterogeneous layer of silicates and oxides of different chemical elements, the mantle has a fairly homogeneous combination of different types of silicates, mainly of magnesium and iron. Geophysical evidence indicates that the core should contain element with the properties of molten iron and some nickel (mean atomic number = 22). It also composes some lighter chemical element like sulfur, carbon, silicon, and oxygen.
Occurrence of Elements in Earth’s Crust
The abundance of different types of chemical elements depends on the mode of occurrence or basic units of substances. Some elements present in the crust in considerable amounts never occur in any concentrated form, pure form of an element dispersed from common minerals. These elements are defined as dispersed elements of the environment. For example, copper is much less abundant than rubidium. Therefore, rubidium is dispersed in potassium minerals, similarly, gallium is dispersed in aluminum minerals but chemical element chromium and lead comparatively less abundant periodic table metal.
The availability of chemical element depends largely on its chemical compounds or minerals composition. Chemically extraction of the element from such dispersed states is impractical for technical and economic reasons. The main forms of existence of common chemical element on earth crust form the compounds like silicates, carbonates, sulfides, sulfates. According to Goldschmidt, the chemical elements are classified into four groups like siderophilic or iron-loving, chalcophile or copper loving, lithophilic or stone loving, and atmophilic or vapour loving periodic table element.