Final answer:
The correct statements describing a polar covalent bond are:
b) Electronegativity difference is 1.8.
d) There is an unequal sharing of electrons.
Step-by-step explanation:
A polar covalent bond occurs when there is an unequal sharing of electrons between two atoms due to differences in electronegativity. Electronegativity is a measure of an atom's ability to attract shared electrons in a covalent bond. Statement b) with an electronegativity difference of 1.8 or greater is correct because a significant difference in electronegativity indicates polar covalent bonding. In polar covalent bonds, electrons are pulled more strongly toward the more electronegative atom, resulting in an uneven distribution of charge.
On the other hand, statement a) with an electronegativity difference of 0.3 is incorrect because such a small difference suggests a nonpolar covalent bond, where electrons are shared nearly equally. Statement c) is also incorrect as electrons in polar covalent bonds are not shared equally; rather, they are attracted more to one atom than the other. Therefore, the correct statements for a polar covalent bond are those where there is a significant electronegativity difference (b) and unequal sharing of electrons (d).
Understanding the electronegativity difference is crucial in predicting the nature of a bond, whether it is nonpolar covalent, polar covalent, or ionic. In polar covalent bonds, the more electronegative atom attracts electrons more strongly, creating partial charges and resulting in a polar molecule.