upolær

Upolær refers to a type of chemical bond or molecule that lacks a significant difference in electronegativity between its constituent atoms. This lack of electronegativity difference means that the electrons involved in the bond are shared relatively equally between the atoms. Consequently, there is no partial positive or negative charge distribution across the bond or molecule, resulting in no net dipole moment.

In a nonpolar covalent bond, the atoms involved have very similar or identical electronegativity values. This leads to an even distribution of electron density. Examples include bonds between identical atoms, such as the O-O bond in O2 or the C-C bond in ethane. Bonds between atoms with only a small electronegativity difference, such as the C-H bond in methane, are also considered nonpolar.

Molecules can be described as nonpolar even if they contain polar bonds. This occurs when the molecular geometry is symmetrical, causing the individual bond dipoles to cancel each other out. For instance, carbon dioxide (CO2) has two polar C=O bonds, but due to its linear structure, the dipoles are opposite and equal, resulting in a nonpolar molecule. Similarly, carbon tetrachloride (CCl4) is nonpolar despite having polar C-Cl bonds because its tetrahedral geometry leads to the cancellation of bond dipoles.

The properties of nonpolar substances are distinct from those of polar substances. Nonpolar molecules tend to have lower melting and boiling points because the intermolecular forces between them (primarily London dispersion forces) are weaker. They are generally insoluble in polar solvents like water but are soluble in other nonpolar solvents. This principle is often summarized by the adage "like dissolves like."