The concept of "chemical element" has long been used by scientists. So, in 1661, R. Boyle uses this definition for substances that, in his opinion, can no longer be decomposed into simpler components - corpuscles. These particles do not change during chemical reactions and can have different sizes and masses.
Later, in 1789, Lavoisier proposed the first table, which included 33 simple solids. At the beginning of the nineteenth century. J. D alton introduces the atomic-molecular hypothesis, on the basis of which J. Berzelius subsequently determines the atomic masses of the then known elements. In 1869 D. I. Mendeleev discovers the periodic system (PS) and the periodic law. However, the modern interpretation of this concept was formed later (after the discoveries of G. Moseley and J. Chadwick). In their works, scientists proved that the charge of the atomic nucleus is equal to the corresponding (ordinal) number of the element in the PS of D. I. Mendeleev. For example: Be (beryllium), serial number - 4, nuclear charge - +4.
Datadiscoveries and scientific works helped to conclude that a chemical element is a type of atoms with the same nuclear charge. Therefore, the number of protons in them is the same. Now 118 elements are known. Of these, 89 are found in nature, and the rest are obtained (synthesized) by scientists. It is worth noting that the International Union of Chemistry (IUPAC) has officially recognized only 112 elements.
Every chemical element has a name and a symbol, which (together with the serial number and relative atomic mass) are recorded in the PS D. I. Mendeleev. The symbols with which the types of atoms with an equal nuclear charge are written are the first letters of their Latin names, for example: oxygen (lat. oxygen) - O, carbon (lat. carbon) - C, etc. If the name of several elements begins with the same letter, then another letter is added to its abbreviation, for example: lead (lat. plumbum) - Pb. These designations are international. New superheavy types of atoms with the same nuclear charge that have been discovered in recent years and are not officially recognized by IUPAC (numbers 113, 115-118) have temporary names.
A chemical element can also exist in the form of a simple substance. Note that the names of simple substances may not coincide with the names of the type of atoms with the same nuclear charge. So, for example, He (helium) in nature exists in the form of a gas, the molecule of which consists of one atom. The phenomenon of allotropy may also occur, when one element can exist in the form of several simple substances (oxygen O2and ozone O3). There is also the phenomenon of polymorphism, ie the existence of several structural varieties (modifications). An example of this is diamond, graphite.
Also, according to their properties, types of atoms with an equal nuclear charge are divided into metals and non-metals. Thus, the chemical element metal has a special crystal lattice and most often gives up external electrons in chemical reactions, forming cations, and non-metal attaches particles, forming anions.
During the course of chemical reactions, the element is preserved, because. there is only a redistribution of elementary particles on the outer shells, while the nuclei of atoms themselves remain unchanged.
It turns out that a chemical element is a combination of a certain kind of atoms with the same nuclear charge and the number of protons, which exhibit characteristic properties.
