**Correct Option: C. Covalent bond** ### Detailed Explanation: 1. **Definition of Bond Types**: - **Ionic Bond**: This type of bond occurs when one atom donates an electron to another atom, resulting in the formation of charged ions. The electrostatic attraction between the positively charged ion (cation) and the negatively charged ion (anion) holds them together. - **Metallic Bond**: In metallic bonds, electrons are not shared or transferred between individual atoms. Instead, they form a "sea of electrons" that are free to move around, which allows metals to conduct electricity and heat. - **Covalent Bond**: A covalent bond is formed when two atoms share one or more pairs of electrons. This sharing allows each atom to attain a stable electron configuration, often resembling that of noble gases. - **Hydrogen Bond**: This is a weaker type of bond that occurs between a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen or nitrogen) and another electronegative atom. It is not characterized by the sharing of electron pairs in the same way as covalent bonds. 2. **Why Covalent Bonds Involve Sharing**: - Atoms have a tendency to achieve a full outer shell of electrons, which is often referred to as the octet rule (for main group elements). By sharing electrons, atoms can effectively fill their outer shells. For example, in a water molecule (H₂O), each hydrogen atom shares one electron with the oxygen atom, allowing all three atoms to achieve a more stable electronic configuration. 3. **Comparison with Other Bonds**: - **Ionic Bonds**: In ionic bonding, there is no sharing of electrons; instead, there is a complete transfer of electrons from one atom to another. This results in the formation of ions, which are held together by electrostatic forces. For example, in sodium chloride (NaCl), sodium donates an electron to chlorine, forming Na⁺ and Cl⁻ ions. - **Metallic Bonds**: Unlike covalent bonds, metallic bonds do not involve sharing between specific pairs of atoms. Instead, the electrons are delocalized and can move freely throughout the metal lattice, which is why metals are good conductors of electricity. - **Hydrogen Bonds**: These are not true bonds in the sense of electron sharing or transfer. They are intermolecular forces that occur due to the attraction between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom. They are significantly weaker than covalent bonds. ### Common Pitfalls: - Students often confuse covalent bonds with ionic bonds due to the terminology of "bonding." Remember that covalent bonds involve sharing, while ionic bonds involve transfer. - It’s also important to note that while hydrogen bonds are crucial in biological systems (like DNA and proteins), they do not involve the sharing of electrons and are much weaker than covalent bonds. ### Revision Summary: - **Covalent bonds** involve the sharing of electron pairs between atoms, allowing them to achieve stable electron configurations. - **Ionic bonds** involve the transfer of electrons, resulting in charged ions. - **Metallic bonds** feature a delocalized "sea of electrons" and do not involve sharing between specific atoms. - **Hydrogen bonds** are weak attractions between molecules and do not involve electron sharing. Understanding these distinctions is crucial for mastering the concepts of chemical bonding in chemistry.