Definition of atom in chemistry
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Definition of Atom in Chemistry
Basic Structure and Composition of Atoms
In chemistry, an atom is the fundamental unit of matter. It consists of a nucleus made up of protons and neutrons, which are held together by the strong nuclear force. Surrounding the nucleus are electrons, which interact with the nucleus through electromagnetic forces. The arrangement of these electrons in quantized orbits gives the atom its volume, and the Pauli exclusion principle prevents atoms from overlapping, allowing atoms to be modeled as hard spheres in many contexts .
Historical and Evolving Definitions of the Atom
The concept of the atom has evolved over time. Originally, the term "atom" meant "indivisible," reflecting the belief that atoms were the smallest possible units of matter. However, scientific discoveries in the late 19th and early 20th centuries revealed that atoms themselves are made up of smaller particles—protons, neutrons, and electrons—making the original definition outdated 46. Despite this, the term "atom" remains widely used, though it no longer implies indivisibility .
The Atom in Chemical Theory
Chemistry relies on a clear and operational definition of the atom. Theoretical definitions must allow for the prediction and measurement of properties that are additive and observable in experiments. Definitions based solely on models like electron orbitals or density domains may not fully capture the measurable properties of atoms in molecules. Therefore, the most accepted definition in chemistry is one that describes the atom as a real entity in space, whose form and structure determine its properties, whether it is free or part of a molecule .
Relationship to Molecules, Elements, and Compounds
The atom is distinct from molecules, elements, and compounds. Atoms are the building blocks of molecules, which are combinations of two or more atoms. Elements are substances made up of only one type of atom, while compounds are made from atoms of different elements bonded together. The current definitions of these terms are considered both philosophically sound and suitable for teaching chemistry .
Conclusion
In summary, an atom in chemistry is the smallest unit of an element that retains the element's chemical properties. It is composed of a nucleus of protons and neutrons, surrounded by electrons. While the concept has evolved from its original meaning of indivisibility, the atom remains a central and well-defined concept in chemistry, essential for understanding the structure and behavior of matter 13456.
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