Inclined relation in the periodic table

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Examples of helical relationships in the periodic table. They are represented by red arrows.

An inclined relationship in the periodic table is the similarity of the properties of several elements , with the relevant elements in the periodic table of the elements each being inclined to one another. This relationship applies to two elements of the second and third periods . These are in particular lithium and magnesium , beryllium and aluminum , as well as boron and silicon . Some similarities can also be found between carbon and phosphorus , which is why phosphorus is also referred to as inorganic carbon. There are also analogies between nitrogen and sulfur and between oxygen and chlorine.

The similarities are mainly evident in the types and properties of the compounds formed by an element. Both magnesium and lithium form a large number of organometallic compounds with covalent bonds that have many similar properties. In comparison, sodium , the element directly below lithium, forms organometallic compounds with a strong ionic structure.

The similarities between beryllium and aluminum are stronger than with lithium and magnesium. The compounds of these two elements to form many non-metals , such as the hydrogen compounds , oxides and chlorides , have very similar properties. Both hydrogen bonds are covalent and polymeric . In comparison, magnesium hydride is ionic .

The similarities of phosphorus to carbon are z. B. in the tendency towards multiple bonds and aromatic rings. An isolobal ion to the cyclopentadienyl anion is the P 5 - ion. Such compounds are not yet known from silicon.

The reason for these similarities lies in the similar size of the ratio of ionic radius and positive charge of the atomic nucleus. The occupation of another electron shell leads to an increase in the atomic radius, which, however, is compensated by the increase in the nuclear charge (which leads to an increase in the effective nuclear charge, through which the electrons are more strongly attracted to the atomic nucleus) by the value 1.

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