What characterizes metallic bonds?

Metallic bonds are primarily characterized by a "sea of mobile electrons" that are delocalized throughout a lattice of positively charged metal ions. In metallic structures, the electrons are not bound to any specific atom but are free to move around, which allows them to conduct electricity and heat efficiently. This mobility contributes to the malleability and ductility seen in metals, as the electron cloud can adjust to accommodate changes in shape without breaking the bond.

In contrast, the other options describe different types of bonding or arrangements. For example, a fixed arrangement of atoms in a lattice structure is typical of ionic or covalent compounds, where atoms are held in place by strong bonding forces. The sharing of electrons between two nonmetal atoms is characteristic of covalent bonds, which differ from metallic bonds as they involve localized electron pairs rather than a delocalized electron sea. Lastly, ionic attraction involves electrostatic forces between positively and negatively charged ions, which is also distinct from the nature of metallic bonding. This context highlights how metallic bonds uniquely feature the movement of electrons surrounding positive ions, setting them apart from other bonding types.