An example of a nonpolar covalent bond. Covalent bond polar and nonpolar

A far from last role at the chemical level of the organization of the world is played by the way of the connection of structural particles, the connection between themselves. The overwhelming number of simple substances, namely nonmetals, have a covalent nonpolar type of bond, with the exception of inert gases. Metals in pure form have a special way of communication, which is realized by means of the socialization of free electrons in the crystal lattice.

All complex substances (except for some organic) have covalent polar chemical bonds. The types and examples of these compounds will be discussed below. In the meantime, it is necessary to find out which characteristic of the atom affects the polarization of the bond.

Electronegativity

Atoms, or rather their nuclei (which, as we know, are positively charged) have the ability to attract and retain the electron density, in particular, in the formation of a chemical bond. This property was called electronegativity. In the periodic table, its value grows in periods and major subgroups of the elements. The value of electronegativity is not always constant and can change, for example, with a change in the type of hybridization into which atomic orbitals enter .

Chemical bonds, species and examples of which will be indicated below, or more precisely, the localization or partial displacement of these bonds to one of the binding agents, is explained precisely by the electronegative characteristics of an element. Displacement occurs to that atom, at which it is stronger.

Covalent nonpolar bond

The "formula" of the covalent nonpolar bond is simple - two atoms of the same nature unite the electrons of their valence shells into a joint pair. Such a pair is called divided because it belongs equally to both parties to the binding. It is due to the socialization of the electron density in the form of a pair of electrons that the atoms go into a more stable state, since they complete their external electronic level, and the "octet" (or "doublet" in the case of a simple hydrogen H ₂ , has a single s-orbital for The completion of which requires two electrons) is the state of the external level to which all atoms aspire, since its filling corresponds to the state with minimum energy.

An example of a nonpolar covalent bond is in the inorganic and, strange as it may sound, but also in organic chemistry too. This type of bond is inherent in all simple substances - nonmetals, apart from noble gases, since the valence level of the inert gas atom has already been completed and has an octet of electrons, which means that it does not make sense for him and even less energetically favorably. In organics, nonpolarity is found in individual molecules of a certain structure and is of a conventional nature.

Covalent polar bond

An example of a nonpolar covalent bond is limited to a few molecules of a simple substance, while dipole compounds, in which the electron density is partially shifted toward a more electronegative element, is the vast majority. Any combination of atoms with different electronegativity gives a polar connection. In particular, bonds in organic matter are covalent polar bonds. Sometimes ionic, inorganic oxides are also polar, and in salt and acid the ionic type of binding prevails.

As an extreme case of polar binding, the ionic type of compounds is sometimes considered. If the electronegativity of one of the elements is significantly higher than the other, the electron pair completely shifts from the center of communication to it. This is how the ions are divided. The one who takes the electronic pair, turns into an anion and receives a negative charge, and the losing electron - turns into a cation and becomes positive.

Examples of inorganic substances with covalent non-polar bonding type

Substances with a covalent nonpolar bond are, for example, all binary gas molecules: hydrogen (H-H), oxygen (O = O), nitrogen (in its molecule, two atoms are bound by a triple bond (N ≡ N)); Liquids and solids: chlorine (Cl - Cl), fluorine (F - F), bromine (Br - Br), iodine (I - I). And also complex substances consisting of atoms of different elements, but with the actual identical value of electronegativity, for example, phosphorus hydride - PH ₃ .

Organics and non-polar binding

It is extremely clear that all organic substances are complex. The question arises, how can a nonpolar bond in a complex substance? The answer is pretty simple, if you think a little logically. If the electronegativity values of the bound elements differ insignificantly and do not create a dipole moment in the compound, such a connection can be considered nonpolar. It is precisely this situation with carbon and hydrogen: all С-Н bonds in organic matter are considered nonpolar.

An example of a nonpolar covalent bond is a molecule of methane, the simplest organic compound. It consists of one carbon atom, which, according to its valence, is bound by single bonds to four hydrogen atoms. In fact, the molecule is not a dipole, since there is no charge localization in it, in some way and due to the tetrahedral structure. The electron density is evenly distributed.

An example of a nonpolar covalent bond is also found in more complex organic compounds. It is realized due to mesomeric effects, that is, sequential retraction of the electron density, which rapidly fades along the carbon chain. Thus, in the hexachloroethane molecule, the C-C bond is nonpolar due to the uniform retraction of the electron density by six chlorine atoms.

Other types of links

In addition to the covalent bond, which, by the way, can also be realized by the donor-acceptor mechanism, ionic, metallic, and hydrogen bonds take place. Brief characteristics of the penultimate two are presented above.

Hydrogen bonding is an intermolecular electrostatic interaction that occurs when a molecule contains a hydrogen atom and any other that has unpaired electron pairs. This type of binding is much weaker than the others, but due to the fact that a great deal can form in the substance of these bonds, it makes a significant contribution to the properties of the compound.