atomien

Atomien are the basic units of chemical elements and the building blocks of matter. An atom consists of a central nucleus containing protons, which carry a positive charge, and neutrons, which are electrically neutral, surrounded by an electron cloud where electrons move and carry a negative charge. The nucleus contains nearly all the atom’s mass and is held together by the strong nuclear force, while the electron cloud governs the atom’s interactions and chemical behavior.

The atomic number Z equals the number of protons and defines the identity of the element. The mass number A, the sum of protons and neutrons, can vary among atoms of the same element, producing isotopes. Isotopes share chemical properties determined by Z but may differ in stability and decay modes. Electrons occupy quantum-mechanical orbitals around the nucleus, and their arrangement, or electron configuration, determines how atoms bond with others and form molecules. The periodic table organizes elements by increasing Z and recurring electron configurations, reflecting trends in reactivity and properties.

Historically, atomic concepts evolved from Dalton’s atomic theory to Thomson’s electron, Rutherford’s nuclear model, and the quantum-mechanical description of electrons. In modern physics, atoms are described within the Standard Model, with protons and neutrons composed of quarks and electrons treated as fundamental leptons. Atoms and their interactions underpin chemistry, materials science, and many technologies, from medicines to electronics.