Chemistry

Chemistry (also spelled kemistari or kimistari; English: chemistry) is the natural science that studies matter—what it is made of, its properties, and the changes it undergoes when substances interact. It is founded on the atom and structures composed of atoms, such as molecules and crystals.

Chemistry occupies a position between physics and biology. Physics examines the general laws of energy and matter, while chemistry focuses on how atoms bond together and form new substances. Biology applies the findings of chemistry to understand the processes of life.

Fundamental Concepts

The atom is the smallest unit of an element that retains its properties. It consists of a nucleus containing protons and neutrons, surrounded by electrons. The number of protons determines the type of element. Elements are arranged in the periodic table, which organizes them by rows and columns according to similarities in their properties.

Chemical bonds hold atoms together. There are several types: ionic bonds, in which electrons are transferred from one atom to another; covalent bonds, in which electrons are shared; and metallic bonds. A chemical reaction is a process in which bonds are broken and new ones are formed, while the total number of atoms remains unchanged.

Major Branches

Chemistry is traditionally divided into: organic chemistry, which studies carbon-based substances; inorganic chemistry, which examines other elements and their compounds; physical chemistry, which uses mathematics and physics to explain reactions and energy; analytical chemistry, which measures and identifies the composition of substances; and biochemistry, which studies the reactions that occur in living organisms.

History

Chemistry has its roots in alchemy, a practice that developed across ancient Egypt, Greece, and the Islamic world. Scholars such as Jabir ibn Hayyan developed experimental methods including distillation and crystallization. In the seventeenth and eighteenth centuries, controlled experiments—notably Antoine Lavoisier's work on the conservation of mass and the role of oxygen—transformed chemistry into a scientific discipline. In the nineteenth century, John Dalton proposed atomic theory, and Dmitri Mendeleev created the periodic table.

Applications

Chemistry underpins the pharmaceutical, agricultural, petroleum, metallurgical, and materials industries. It is also used in environmental analysis, food preservation, and energy technology such as batteries. At the same time, it has raised concerns related to chemical toxicity and pollution, leading to the development of international regulatory standards.