Hydrogen bonds are formed when:
- b) electrons are shared unequally by atoms
Explanation: Hydrogen bonds occur when a hydrogen atom, which is covalently bonded to a more electronegative atom (such as oxygen or nitrogen), experiences an attraction to another electronegative atom nearby. In this scenario, the electrons are not shared equally between the atoms involved in the bond, resulting in partial positive and negative charges. This unequal sharing creates a dipole, allowing the positively charged hydrogen to attract to the negatively charged region of another molecule, thus forming the hydrogen bond. This interaction plays a crucial role in the properties of water and in various biological molecules, such as DNA.