A covalent polar bond is one of the types of chemical bonds between atoms of a substance, due to which molecules are formed. If there are no problems with understanding with the word “connection”, the terms “covalent” and “polar” are not known to an unprepared person (of course, provided that the school chemistry program has not been forgotten).
So, the word “covalent” is derived from “co-” and “-valent”, which literally means a mutually directed force. Indeed, this is the force that is able to combine two atoms into a molecule by reconfiguring their electronic shells into a single structure. Since both nuclei become equal, the electrons rotating around them fill not only the “external” sides, but also the gap between the atoms. We can say that it is he who is a covalent bond. Moreover, such a dual system tends to the completeness of the electronic configuration, since charge carriers supplement the shells of interacting atoms. Note that only a pair of electrons implements this type of bond.
Another variant of the same phenomenon can be called the ionic type of bond. Since an ion is formed when an atom loses an electron, it arises from the exchange of negative charge carriers, which is typical for atoms of different substances (for example, fluorine and sodium).
Polar covalent bond is an intermediate option. This variety resembles a “purely covalent” one in that a molecular orbital (a union of orbits) is formed, and from the ionic in it a partial “pulling” of charge carriers. The pair is shifted to one of the atoms, but does not completely leave the zone of the other. An example in which a covalent polar bond is involved is a water molecule. Completed shells are created by combining one oxygen atom and two hydrogen. However, since oxygen has a more pronounced property of attracting electrons, their pair is shifted precisely to the "O" nucleus. By the way, it is not necessary that atoms form one pair of electrons: there can be two, three, etc. The covalent polar bond in the system creates a charge distribution (partial) and, as a result, polarity. The orientation of the molecule is observed according to the lines of field strength. We can say that due to this distribution, a peculiar molecular dipole arises. His moment (mu) forms an electric field and tension. There are a number of formulas for calculating the dipole moment (in particular, the product of the distance by the charge), they allow you to calculate the polarity of the formed molecule.
In other words, a covalent polar bond can be formed by atoms, the electronegativity of which, although different, is not enough to form an ionic bond. Let us explain what electronegativity is. This term indicates the ability of a particular atom to attract to its core the formed (s) pair of negative charge carriers. Obviously, in accordance with the law of conservation of energy, the more interatomic bonds, the less their length. Usually, a covalent polar bond is characteristic of atoms whose chemical characteristics are similar. It is characterized by spatial orientation. Thanks to this, it is possible to form not only molecules, but also crystal lattices in which atoms are placed in the geometrically correct order.
Since the bond, in fact, is the superposition of two (or more) electron clouds on one another, belonging to different atoms, its strength mainly depends on how much the superposition takes place. It is easy to understand that due to the creation of pairs, the electron density increases in the internuclear gap.