How do non-polar covalent bonds arise

Covalent bonding explained in simple terms: example, difference, electronegativity

Atoms can reach a more energetically favorable position through bonds. In addition to the ionic bond and the metallic bond, there is also the covalent bond.

A particularly favorable one is the noble gas configuration with 2 (helium) or 8 valence electrons. There are several ways to achieve the electron octet.

Covalent bonds or electron pair bonds come about when atoms share (at least) one electron pair, whereby both atoms reach the octet.

Example of a covalent bond

As an example, consider elemental fluorine (F2):

Each of the two fluorine atoms has 7 valence electrons. For fluorine, it would be energetically worthwhile if the two atoms shared a pair of electrons. The result is that a molecule is created that has an octet of electrons.

Two fluorine atoms share a pair of electrons, creating one Covalent bond arises. However, a single bond does not have to be present in a covalent bond. Of course, double and triple bonds can also be shared by the individual atoms, as is the case with elemental nitrogen (N2).

Difference to the ion compound

A covalent bond can be distinguished from an ionic bond in that the electronegativity difference of of the atoms involved is not particularly large. Usually in the literature a value of < 1,7="" für="" kovalente="" bindungen="" angegeben.="" oberhalb="" dieser="" grenze="" geht="" man="" von="" ionischen="" verbindungen="" aus.="">

Electronegativity and covalent bonds

Covalent bonds can be further subdivided among each other. A criterion or measure for this subdivision is that polarity. This describes the distribution of the shared electrons between the binding partners.

The electrons can either be distributed equally (symmetrically) between the binding partners or unevenly (asymmetrically).

In the unbalanced The division of electrons can also be used to determine which binding partner attracts the electrons more strongly. To assess the binding polarity one has to consider the electronegativities of the individual binding partners.

The Electronegativity describes the ability of an atom to attract electrons in a bond. The higher the electronegativity of an atom, the more strongly this atom will attract the common electrons in a bond.

Non-polar and polar covalent bonds

If both binding partners in a covalent bond have the same electronegativity, the partners attract the common electrons equally. This results in a non-polar covalent bond. Non-polar means that the charge distribution within the molecule is balanced and no pole is formed in which the electron density would be higher than expected. Non-polar covalent bonds always occur when, for example, only atoms of one element are involved in a bond, as is the case with a fluorine or oxygen molecule.

You can use the same principle polar covalent bonds define. In these, the electronegativity difference is not equal to zero, but less than 1.7, since otherwise it would be an ionic compound. An example of a polar covalent bond would be HBr (hydrogen bromide). In this case the bromine with an electronegativity of 2.8 is more electronegative than the hydrogen with 2.1.

This fact is indicated with the following notation:

The “plus” indicates that the hydrogen is less electronegative (more electropositive) than the bromine. Alternatively, the polarity can also be indicated by a small delta followed by a “plus” above the hydrogen atom or by a delta followed by a “minus” above the bromine atom.

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