Concept

Chemical element

Overview

A chemical element is a species of atom defined by its number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's atomic number. Almost all baryonic matter in the universe is composed of elements (among rare exceptions are neutron stars).

The term "chemical element" is also widely used to mean a pure chemical substance consisting of a single element. For example, oxygen gas consists only of atoms of oxygen.

Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity. There was some controversy in the 1920s over whether isotopes deserved to be recognised as separate elements if they could be separated by chemical means. By November 2016, the International Union of Pure and Applied Chemistry (IUPAC) recognized a total of 118 elements. The first 94 occur naturally on Earth, and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements (radioelements) which decay quickly, nearly all elements are available industrially in varying amounts. The discovery and synthesis of further new elements is an ongoing area of scientific study.

The history of the discovery and use of elements began with early human societies that discovered native minerals such as carbon, sulfur, copper, and gold (though the modern concept of an element was not yet understood). Attempts to classify materials such as these resulted in the concepts of classical elements, alchemy, and similar theories throughout history. Much of the modern understanding of elements developed from the work of Dmitri Mendeleev, a Russian chemist who published the first recognizable periodic table in 1869. This table organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. The periodic table summarizes various properties of the elements, allowing chemists to derive relationships between them and to make predictions about exceedingly transient nuclides not yet observed, and the potential compounds these unknown elements might form.

Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).

Possible passages

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And a node (ὄζος) of gold, rendered by its density very hard and turned black, is called _adamant_.
Plato, The works of Plato
States what Chemical element is; the author is tied to Chemical element in the knowledge graph.
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The liquid is composed of small and unequal particles, the fusile of large and uniform particles and is more solid, but nevertheless melts at the approach of fire, and then spreads upon the earth. When the substance cools, the fire passes into the air, which is displaced, and forces together and condenses the liquid mass. This process is called cooling and congealment. Of the fusile kinds the fairest and heaviest is…
Plato, Timaeus
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Substance, in the truest and primary and most definite sense of the word, is that which is neither predicable of a subject nor present in a subject; for instance, the individual man or horse. But in a secondary sense those things are called substances within which, as species, the primary substances are included; also those which, as genera, include the species. For instance, the individual man is included in the…
Aristotle, The Categories
States what Chemical element is; the author is tied to Chemical element in the knowledge graph.
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Philosophers who discussed Chemical element

Paracelsus

Related ideas

Place in the tradition

Part of Lebensphilosophie.

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