**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 a true bond in the sense of electron sharing or transfer. 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. This sharing allows the oxygen to have a total of eight electrons in its outer shell (six from itself and one from each hydrogen), while each hydrogen achieves a stable configuration with two electrons. 3. **Why Other Options Are Incorrect**: - **A. Ionic Bond**: This option is incorrect because ionic bonds involve the transfer of electrons rather than sharing. In ionic bonding, one atom loses electrons and becomes positively charged, while another atom gains those electrons and becomes negatively charged. - **B. Metallic Bond**: This option is also incorrect because metallic bonds do not involve sharing of electrons between specific atoms. Instead, they involve a delocalized pool of electrons that are free to move throughout the metal lattice. - **D. Hydrogen Bond**: This option is incorrect as well because hydrogen bonds are not true bonds formed by electron sharing. They are weak attractions between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom. ### Summary of Key Points: - **Covalent bonds** involve the sharing of electron pairs between atoms, allowing them to achieve stable electron configurations. - **Ionic bonds** involve the transfer of electrons, leading to the formation of charged ions. - **Metallic bonds** consist of a delocalized sea of electrons, not shared pairs. - **Hydrogen bonds** are weak attractions and do not involve direct sharing of electrons. ### Revision Summary: - Covalent bonds = sharing of electron pairs. - Ionic bonds = transfer of electrons, forming ions. - Metallic bonds = delocalized electrons, not shared. - Hydrogen bonds = weak attractions, not true bonds.