A covalent bond in which electrons are shared equally is called a non-polar covalent bond. In a non-polar covalent bond, the atoms involved have similar electronegativities, meaning that they have a similar attraction for electrons. This results in the electrons being shared equally between the atoms, and neither atom has a partial positive or negative charge.

Examples of non-polar covalent bonds include the bonds between two hydrogen atoms (H-H), two chlorine atoms (Cl-Cl), and two carbon atoms (C-C). In these cases, the atoms involved have similar electronegativities and the electrons are shared equally between them.

In contrast, a polar covalent bond is a covalent bond in which the electrons are shared unequally between the atoms. This occurs when the atoms involved have different electronegativities, meaning that one atom has a greater attraction for electrons than the other. This results in the electrons being pulled towards the more electronegative atom, and the bond has a partial positive charge on the less electronegative atom and a partial negative charge on the more electronegative atom.

Examples of polar covalent bonds include the bonds between hydrogen and chlorine (H-Cl), hydrogen and oxygen (H-O), and carbon and oxygen (C-O). In these cases, the electronegativity difference between the atoms results in the electrons being shared unequally, and the bonds have a partial positive and negative charge.