See also: Element
From an atomic point of view, a chemical element (or simply a element ) is the whole of the Atome S which have the same number of Proton S in their core. This number is called Atomic number element (or number of load , Z).
This term also indicates is a pure substance made up of atoms having the same number of Proton S and which thus cannot be broken up. A chemical element cannot be transformed into another element by a Chemical reaction, such a transformation requires a nuclear Reaction. This modern definition, in opposition to the theory Plato ician of the four elements, was introduced by Robert Boyle in 1661. Indeed, a chemical reaction brings into play the bonds between the external electron S of the atoms, whereas a nuclear reaction modifies the Nucléon S of the atomic nucleus. The chemical properties are determined by the electronic structure of the atom, and depend directly on the atomic number (see hereafter).
Currently one knows 117 elements (1 with the 118, except for the 117) of which 94 exist in a natural state on Ground. These elements are commonly distributed in a periodic table invented by Mendeleïev and named the periodic Tableau of the elements.
Concept of elementsThis concept was introduced to gather between them the matters having similar chemical properties.
IsotopesThe atoms which have the same number of protons but a number different of Neutron S are called Isotope S. the protons and the neutrons constitute collectively the Nucléon S, the particles of the atomic nucleus. The full number of nucleons of a core is called mass number , NR. When one is interested in the isotope, one indicates it like name of the element - mass number . For example, Carbon-14 celebrates it is the isotope of mass number 14 of carbon. Certain elements have an isotope much more spread than the others in nature. Thus, carbon presents to 98,9% pennies the isotope carbon-12, to 1,1% like carbon-13, and radioactive carbon-14 is present only at the state of trace. Others have one stable isotope, like fluorine (100% of fluorine-19), and others, finally, consist of two or several isotopes present in considerable quantities, as copper (copper-63: 69%, copper 65: 31%).
Combinations of the elementsThe chemical elements (atoms) can combine in very variable ways. In pure form, they can be presented in particular like atoms separated, Molécule S including/understanding several Atome S of the same element, in the form of crystalline solids or amorphous. In the form of molecular compounds, the atoms are gathered in molecules with a number and a precise fitting of atoms of various elements. The elements can also be mixed in chemical forms of compounds less strictly organized, like metal Alliage S.
Names and notation of the elements
The origin of the namesThe names of the chemical elements vary according to the languages. All the elements have on the other hand a single symbol, made up of a letter Majuscule, and possibly of a small letter. The Carbone for example is noted C , and the Sodium Na (of Latin Natrium ). The names of the elements often go back to before their classification by science like elements (in opposition to the compounds mixing several elements). For example, lead " was called; plomb" well before having this would be only the concept of element chemical. The names come from very diverse fields:
- the Mythology: tantalum, mercury, Thorium, Niobium.
- colors: chromium, Rubidium, Chlorine.
- the Geography: Polonium, Germanium, Francium, europium.
- the name of their discoverer or a famous scientist: Curium, Fermium, Bohrium the elements recently discovered, always of the elements heavy, unstable, and artificial, are named after their discovery by the International union of chemistry pure and applied (UICPA).
NotationOne notes an element by his symbol possibly supplemented of indices and exhibitors when one speaks about a precise atom or ion:
- the mass number is noted by exposing symbol (ex on the left: 14 C for carbon-14). It makes it possible to distinguish the isotopes.
- One can note, always on the left, in index the atomic number, but it is redundant with the symbol. One could thus note C for carbon, but it is normally useless, C already stating that the atomic number is 6. This notation is thus used when the atomic number of the element has an importance and being known of the reader is not supposed.
- the index on the right indicates the quantity of the element in a molecule. For example, indicates the molecule of Eau, made up of two atoms of Hydrogène (symbol H, and the 2 in index indicating their number), and of an atom of Oxygène (symbol O, one does not note the 1 who is implicit).
- When one speaks about an ion, the exhibitor on the right indicates the electric Charge carried by this one. Fe 2+ indicate the ion Fer (II). The ion Oxonium (or Hydronium), which carries a positive load, is noted + , there still, the 1 front the plus sign (or signs it less) is implicit.
- Discovered chemical elements
- List of the chemical elements
- List of the chemical elements, sorted by melting point
- Table of the isotopes
- periodic Table of the elements
- Database of the French company of Chemistry (SFC)
Simple: Chemical element Zh-min-nan: Hoà-ha̍k goân-sò͘ Zh-yue: 元素
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