The correct option is **C. Covalent bond**. ### Detailed Explanation: 1. **Definition of Covalent Bond**: A covalent bond is formed when two atoms share one or more pairs of electrons. This sharing allows each atom to attain the electron configuration of a noble gas, leading to greater stability. Covalent bonds typically occur between nonmetal atoms. 2. **How Covalent Bonds Form**: - Atoms have electrons in shells around their nucleus. The outermost shell, known as the valence shell, determines how an atom interacts with others. - Atoms tend to be more stable when they have a full valence shell, which usually contains eight electrons (the octet rule). - To achieve this stability, atoms can share electrons. For example, in a water molecule (H₂O), each hydrogen atom shares one electron with the oxygen atom, allowing all involved atoms to have a more stable electron configuration. 3. **Types of Covalent Bonds**: - **Single Bond**: Involves the sharing of one pair of electrons (e.g., H₂). - **Double Bond**: Involves the sharing of two pairs of electrons (e.g., O₂). - **Triple Bond**: Involves the sharing of three pairs of electrons (e.g., N₂). 4. **Characteristics of Covalent Bonds**: - They can form between identical atoms (e.g., Cl₂) or different atoms (e.g., CO₂). - Covalent compounds generally have lower melting and boiling points compared to ionic compounds. - They do not conduct electricity in the solid state because there are no free-moving charged particles. ### Why Other Options Are Incorrect: - **A. Ionic Bond**: - An ionic bond is formed when one atom donates an electron to another atom, resulting in the formation of charged ions (cations and anions). These oppositely charged ions attract each other. This process does not involve sharing electrons but rather a transfer of electrons, which is fundamentally different from covalent bonding. - **B. Metallic Bond**: - Metallic bonds occur between metal atoms where electrons are not shared or transferred in the traditional sense. Instead, they form a "sea of electrons" that are free to move around, allowing metals to conduct electricity and heat. This type of bonding does not involve the sharing of electron pairs between specific atoms. - **D. Hydrogen Bond**: - A hydrogen bond is a weak attraction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen or nitrogen) and another electronegative atom. While it involves interactions between molecules, it is not a bond formed by the sharing of electron pairs between atoms in the same way that covalent bonds are. ### Summary of Key Points: - A covalent bond involves the sharing of electron pairs between atoms, leading to stability. - Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs. - Ionic bonds involve electron transfer, metallic bonds involve a sea of electrons, and hydrogen bonds are weak attractions, not true bonds formed by sharing electrons. - Understanding the differences between these types of bonds is crucial for grasping the fundamentals of chemical bonding and molecular structure.