Polar covalent bond

Definition

A polar covalent bond is a type of chemical bond that occurs when two atoms share electrons unequally, resulting in a molecule with a partial positive charge on one side and a partial negative charge on the other. This unequal sharing happens when the atoms involved have different electronegativities, meaning one atom has a stronger pull on the shared electrons than the other. The presence of a polar covalent bond leads to molecular polarity, which has significant effects on the physical and chemical properties of substances.

5 Must Know Facts For Your Next Test

1. In a polar covalent bond, the difference in electronegativity between the two bonded atoms typically ranges from 0.4 to 1.7 on the Pauling scale.
2. Common examples of polar covalent bonds include the bonds in water (H₂O), where oxygen is more electronegative than hydrogen.
3. The polarity of a molecule can affect its solubility in various solvents, with polar molecules generally dissolving well in polar solvents like water.
4. Polar covalent bonds can lead to hydrogen bonding when molecules with polar covalent bonds interact with each other, significantly affecting boiling and melting points.
5. Molecules with polar covalent bonds often have distinct physical properties compared to nonpolar molecules, such as higher boiling points and greater reactivity.

Review Questions

• How does electronegativity influence the formation of polar covalent bonds?
  • Electronegativity plays a crucial role in forming polar covalent bonds as it determines how strongly an atom attracts shared electrons. When two atoms with differing electronegativities form a bond, the atom with higher electronegativity pulls the shared electrons closer, resulting in an unequal distribution of charge. This charge separation leads to partial positive and negative charges within the molecule, making it polar.
• Compare and contrast polar and nonpolar covalent bonds in terms of their properties and implications for molecular behavior.
  • Polar covalent bonds involve unequal sharing of electrons, resulting in partial charges that create dipoles within molecules, influencing their solubility and reactivity. In contrast, nonpolar covalent bonds involve equal sharing of electrons, leading to molecules that do not have dipoles. This difference affects their interactions with other substances; polar molecules tend to dissolve well in polar solvents while nonpolar molecules do better in nonpolar solvents.
• Evaluate the significance of polar covalent bonds in biological systems, particularly in water's role as a solvent.
  • Polar covalent bonds are essential in biological systems, particularly due to water's unique properties resulting from its polar nature. The hydrogen-oxygen polar covalent bonds give water its high boiling point and ability to dissolve many ionic and polar substances. This makes water an excellent solvent for biochemical reactions, enabling crucial processes such as nutrient transport and metabolic reactions within cells. The polarity also facilitates hydrogen bonding between water molecules, contributing to its cohesive and adhesive properties, which are vital for various biological functions.

Related terms

Electronegativity:

A measure of the tendency of an atom to attract a bonding pair of electrons, which determines how electrons are shared in covalent bonds.

Nonpolar covalent bond: A type of covalent bond where two atoms share electrons equally, resulting in no charge separation within the molecule.

Molecular polarity: The distribution of electric charge across a molecule, which can be influenced by the presence of polar covalent bonds and their arrangement in three-dimensional space.