What is a covalent polar bond

Covalent polar bonding is one of the types of chemical bond between the atoms of matter, through which molecules are formed. If the word "connection" does not raise problems with understanding, then the terms "covalent" and "polar" to the unprepared person are unknown (of course, provided that the school chemistry program is not 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, reconfiguring their electronic shells into a single structure. Since both nuclei become equal, the electrons rotating around them fill not only the "outer" sides, but also the gap between the atoms. We can say that it is the covalent bond. In this case, such a doubled system tends to completeness of the electron configuration, since charge carriers supplement the shells of interacting atoms. Note that only a pair of electrons realizes this kind of connection.

Another variant of this phenomenon is the ionic type of bond. Since an ion is formed when an atom loses an electron, it arises when carriers exchange a negative charge, which is characteristic of atoms of different substances (eg, fluorine and sodium).

The polar covalent bond is an intermediate variant. This kind of reminiscent of "purely covalent" in that a molecular orbital (a combination of orbits) is formed, and from ionic in it a partial "tug-of-war" of charge carriers. The pair moves to one of the atoms, but does not completely leave the zone of the other. An example in which a covalent polar bond is a molecule of water. Completed shells are created by combining one oxygen atom and two hydrogen atoms. However, since oxygen has a more pronounced property of attracting electrons, their pair is shifted to the "O" core. By the way, atoms do not necessarily form one pair of electrons: they can be two, three, etc. The covalent polar bond creates in the system a charge distribution (partial) and, as a consequence, polarity. The orientation of the molecule is observed according to lines of field strength. It can be said that due to this distribution a peculiar molecular dipole arises. Its 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 per charge), they make it possible to calculate the value of the polarity of the formed molecule.

In other words, a covalent polar bond can be formed by atoms whose electronegativity, although different, is not enough to form an ionic bond. Let us explain what is electronegativity. This term indicates the ability of an atom to attract to its nucleus the formed pair of carriers of a negative charge. Obviously, in accordance with the law of conservation of energy, the more interatomic bonds, the smaller their length. Typically, 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 the atoms are placed in a geometrically correct order.

Since the connection, in fact, is a superposition of two (or more) electron clouds belonging to different atoms, its strength mainly depends on how much overlap occurs. It is not difficult to understand that due to the creation of pairs, in the internuclear gap the value of the electron density increases.