Main group
In chemistry , main groups are those groups in the periodic table that belong to the s and p blocks of the periodic table .
| IUPAC group | Main group | content |
|---|---|---|
| 1 | I. | Alkali metals |
| 2 | II | Alkaline earth metals |
| 13 | III | Boron group |
| 14th | IV | Carbon-silicon group |
| 15th | V | Nitrogen-phosphorus group |
| 16 | VI | Chalcogens |
| 17th | VII | Halogens |
| 18th | VIII | Noble gases |
The arrangement of the chemical elements in the periodic table was made in such a way that elements with similar properties are each grouped together, i.e. H. the columns in the periodic table contain elements with similar chemical properties. The agreement is greatest in the main groups. The periodic table of the elements consists of eight main groups and ten subgroups . The main group indicates how many electrons are on the outermost shell of an atom .
The agreement between the properties of the alkali metals, alkaline earth metals, halogens and noble gases is particularly clear:
The elements of the alkali metals are lithium , sodium , potassium , rubidium , cesium and francium . Hydrogen is in the same main group, but due to its physical and chemical properties it cannot be counted among the alkali metals. The alkali metals have a low melting temperature, react quickly and violently with water (with the formation of hydrogen gas and the corresponding alkali) and oxygen , have low densities , are all flammable light metals and show characteristic flame colors. The alkali metals do not occur elementally in nature, but only in compounds. The elementary metals from lithium to potassium are stored in or under petroleum and are soft metals that can be cut. Rubidium and cesium are stored in ampoules and largely melt when the hands are warm. Their salts, like the elementary metals, show characteristic colors in the burner flame.
The alkaline earth metals show a behavior similar to the alkali metals , but are weakened in all properties. This group includes beryllium , magnesium , calcium , strontium , barium and radium . In contrast to the alkali metals, however, they (with the exception of beryllium and magnesium) form poorly soluble carbonates and sulfates .
The elements of the halogens , which are also called salt formers, are fluorine , chlorine , bromine , iodine , astatine and tenness . These elements also occur in nature only in compounds and react violently with hydrogen gas (to acids), metals (to salts) and are also colored and harmful to health. Since fluorine and chlorine react very quickly and aggressively in air , one should be careful when trying them.
The elements of the noble gases are helium , neon , argon , krypton , xenon and radon . They only occur elementarily in nature. The noble gases are odorless, colorless and gaseous. They are only present in small quantities in the air and hardly react with other substances; a property that they have in common with precious metals . That is why they are called noble gases. Nothing is known about the noble gas character of the artificial element Oganesson , which belongs to the same group , since only a few atoms have been produced so far, but it could differ from the typical noble gases due to relativistic effects.
The fact that the elements of the main groups have similar properties is related to the structure of the atoms. The main group elements try to achieve a noble gas configuration of the electron shell through reactions with other substances . Elements in the same main group must donate or accept the same number of electrons in order to achieve this; therefore the same properties result.
Web links
literature
- Charles E. Mortimer, Ulrich Müller, Johannes Beck: Chemistry: the basic knowledge of chemistry . 12th, corrected and updated edition. Georg Thieme Verlag, Stuttgart, New York 2015, ISBN 978-3-13-484312-5 .