The least polar bond is a nonpolar covalent bond. A nonpolar covalent bond occurs when the electrons are equally shared between the atoms involved in the bond, resulting in no significant separation of charge and an overall neutral distribution of electron density.
The degree of polarity in a bond depends on the electronegativity difference between the atoms involved. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. When the electronegativity difference between two atoms is very small or nonexistent, the bond is considered nonpolar.
For example, a bond between two atoms of the same element, such as H2 (hydrogen gas) or O2 (oxygen gas), is nonpolar because the electronegativity difference is zero. Additionally, bonds between atoms with similar electronegativities, such as C-H (carbon-hydrogen) or C-C (carbon-carbon) bonds in organic compounds, are typically nonpolar due to the small electronegativity difference.
In summary, the least polar bond is a nonpolar covalent bond, where there is little or no electronegativity difference between the atoms involved, resulting in an equal sharing of electrons.