Which type of bonding involves metals in a crystal lattice held together by a cloud of delocalized valence electrons?

• A. Ionic
• B. Metallic
• C. Covalent
• D. Hydrogen

Answer: (B)

Metallic bonding involves metals in a crystal lattice held together by a cloud of delocalized valence electrons. In metals, some outer electrons detach from individual atoms and form a free-moving sea that surrounds the positively charged metal ions. This electron cloud binds the lattice together through electrostatic attraction between the mobile electrons and the fixed ions, giving metals their characteristic properties. The delocalized electrons explain why metals conduct electricity in the solid state and why they are malleable and ductile—the lattice can slide without breaking because the electron sea can rearrange to accommodate flow and deformation. In contrast, ionic bonding comes from transferring electrons to form a lattice of oppositely charged ions, covalent bonding involves localized sharing of electrons between specific atoms, and hydrogen bonding is a special dipole interaction involving hydrogen with highly electronegative atoms—none of these feature a sea of delocalized electrons binding a metal lattice.