Variations in electronegativity prompt in the unequal halves of electrons in polar molecules because when one atom is more electronegative than the other, it becomes more polar than the other.
It results in the more electronegative atom to have a slightly negative (-ve) charges, and the other atom to have partial or slightly positive(+ve) charges.
Polar molecules have unequal sharing of electrons because the atoms have unequal attraction for electrons so the sharing is unequal.
The larger the difference in electronegativity between the two atoms, the more the polar the bond.
Hydrogen bonds are involved in unequal sharing of electrons between two atoms.
To know more about variations in electronegativity in polar molecules here :
The number of electrons in the outermost shell of a particular atom determines its reactivity, or tendency to form chemical bonds with other atoms. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.
