Chemistry

Chemistry

 Chemistry, the science that deals with the properties, composition, and structure of substances (defined as elements and compounds), the transformations they undergo, and the energy that is released or absorbed during these processes. Every substance, whether naturally occurring or artificially produced, consists of one or more of the hundred-odd species of atoms that have been identified as elements. Although these atoms, in turn, are composed of more elementary particles, they are the basic building blocks of chemical substances; there is no quantity of oxygen, mercury, or gold, for example, smaller than an atom of that substance. Chemistry, therefore, is concerned not with the subatomic domain but with the properties of atoms and the laws governing their combinations and how the knowledge of these properties can be used to achieve specific purposes.

The great challenge in chemistry is the development of a coherent explanation of the complex behaviour of materials, why they appear as they do, what gives them their enduring properties, and how interactions among different substances can bring about the formation of new substances and the destruction of old ones. From the earliest attempts to understand the material world in rational terms, chemists have struggled to develop theories of matter that satisfactorily explain both permanence and change. The ordered assembly of indestructible atoms into small and large molecules, or extended networks of intermingled atoms, is generally accepted as the basis of permanence, while the reorganization of atoms or molecules into different arrangements lies behind theories of change. Thus chemistry involves the study of the atomic composition and structural architecture of substances, as well as the varied interactions among substances that can lead to sudden, often violent reactions.

Chemistry also is concerned with the utilization of natural substances and the creation of artificial ones. Cooking, fermentation, glass making, and metallurgy are all chemical processes that date from the beginnings of civilization. Today, vinyl, Teflon, liquid crystals, semiconductors, and superconductors represent the fruits of chemical technology. The 20th century saw dramatic advances in the comprehension of the marvelous and complex chemistry of living organisms, and a molecular interpretation of health and disease holds great promise. Modern chemistry, aided by increasingly sophisticated instruments, studies materials as small as single atoms and as large and complex as DNA (deoxyribonucleic acid), which contains millions of atoms. New substances can even be designed to bear desired characteristics and then synthesized. The rate at which chemical knowledge continues to accumulate is remarkable. Over time more than 8,000,000 different chemical substances, both natural and artificial, have been characterized and produced. The number was less than 500,000 as recently as 1965.

Intimately interconnected with the intellectual challenges of chemistry are those associated with industry. In the mid-19th century the German chemist Justus von Liebig commented that the wealth of a nation could be gauged by the amount of sulfuric acid it produced. This acid, essential to many manufacturing processes, remains today the leading chemical product of industrialized countries. As Liebig recognized, a country that produces large amounts of sulfuric acid is one with a strong chemical industry and a strong economy as a whole. The production, distribution, and utilization of a wide range of chemical products is common to all highly developed nations. In fact, one can say that the “iron age” of civilization is being replaced by a “polymer age,” for in some countries the total volume of polymers now produced exceeds that of iron.

 

Why Are MINERALS Important?

Periodic table

 Periodic table 

This is a chart that shows all the known chemical elements. The table is made up of over a hundred squares. Each square represents one element. A square contains one or two letters that stand for the element’s name, and numbers that tell about that element’s properties.

The location of each square in the table tells many things about each element. First, the elements are organized by atomic number, or how many protons they have. Those on top of the chart have the fewest protons. An element’s place also shows how likely it is to react. It also shows how its electrons are arranged.

During the mid-1800s, many chemists looked for patterns that explained how elements interacted. Back then, scientists didn’t know about the protons, neutrons and electrons that make up atoms. But they did understand that elements had different atomic weights.  An atomic weight is the average weight of one atom of an element.

In 1869, the Russian chemist Dimitri Mendeleev lined up the 63 known elements in order by their atomic weights. He saw trends in the elements’ properties that varied over specific intervals, or periods. Other scientists were working on their own periodic tables, but Mendeleev published his table first.

The periodic table continued to grow as scientists discovered more elements. These include the noble gases, identified in 1890. This is a group of elements such as helium that don’t like to react with other elements. Starting in the 1940s, scientists found many new elements by colliding atoms or pieces of atoms.

At the end of 2018, chemists confirmed four elements that had never been observed before. That brought the number of known elements to 118 and completed the 7th row of the table.