Elementer

Elementer, or chemical elements, are the fundamental substances that make up all matter. Each element consists of atoms with a specific number of protons, known as the atomic number, which defines its identity. Elements cannot be broken down into simpler substances by ordinary chemical reactions, though they can combine with others to form compounds.

The elements are arranged in the periodic table, organized by increasing atomic number and by recurring chemical properties. They are broadly classified into metals, nonmetals, and metalloids, with groups such as alkali metals, halogens, and noble gases sharing characteristic behaviors. The table also reflects trends in reactivity, electronegativity, and electron configuration.

Most elements have multiple isotopes—variants with different numbers of neutrons but the same number of protons. Isotopes differ in mass and stability; some are stable, others radioactive and decay over time. The atomic structure, including electron shells, determines an element's chemical behavior and bonding patterns.

Elements occur throughout the universe, from stars to the oceans. The most abundant in Earth's crust are oxygen, silicon, and aluminum; heavier elements are produced in stellar nucleosynthesis. Humans obtain and use elements in industry, medicine, and technology, often in compounds rather than in pure form.

Nomenclature is governed by IUPAC, with each element assigned a unique symbol. The history of element discovery spans ancient times to the modern era, with Dmitri Mendeleev organizing the first predictive periodic table in 1869. Names reflect properties, places, or scientists, and many elements have multiple common names in different languages.

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