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 achieve 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). ### 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. The electrostatic attraction between the positively charged ion (cation) and negatively charged ion (anion) holds them together. This process does not involve sharing electrons but rather a transfer of electrons. - **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, which gives metals their characteristic properties like conductivity and malleability. 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 true bond formed by the sharing of electron pairs. ### Summary of Key Points: - **Covalent bonds** involve the sharing of electron pairs between atoms, leading to stability. - They can form single, double, or triple bonds depending on the number of electron pairs shared. - **Ionic bonds** involve electron transfer, **metallic bonds** involve a sea of delocalized electrons, and **hydrogen bonds** are weak attractions, not true bonds. - Understanding the nature of these bonds is crucial for grasping chemical interactions and molecular structures. This comprehensive understanding of covalent bonds and their distinction from other types of bonds is essential for mastering chemistry concepts.