S2.3 The metallic model

Metallic bonding forms when metal atoms lose their valence electrons, becoming positive cations arranged in a regular lattice. The released electrons become delocalized and move freely throughout the structure.

Sodium (Group 1) loses its single valence electron, forming ${\text{Na}}^{+}$ cations in a lattice. The released electron joins the delocalized electron sea that surrounds and moves between all the cations.

The correct description is: a regular lattice of positive sodium ions surrounded by a sea of delocalized electrons. This captures all three essential features: positive cations, regular lattice arrangement, and delocalized electrons.

The question asks for the correct structural description of a metal — specifically sodium. We need to apply our knowledge of metallic bonding.

Sodium anions are negatively charged — metals form cations (positive ions) when they lose electrons, not anions. Protons are also not mobile particles in a metal lattice. This option is incorrect.

Covalent bonding involves localized electron pairs shared between specific atoms. Metals do not form covalent bonds in this way; their electrons are delocalized throughout the whole structure, not localized between pairs.

Alternating positive and negative ions describes an ionic lattice (like NaCl), not a metal. In a metal, all ions are positive — there are no negative ions in the lattice.

The remaining option — a regular lattice of positive sodium ions surrounded by a sea of delocalized electrons — correctly describes metallic bonding with all three key features present.

The ability to be bent without shattering is malleability (or ductility). The question asks for the structural explanation from the metallic bonding model.

When a force is applied, layers of cations slide past one another. Because metallic bonding is non-directional, the delocalized electron sea simply flows with the displaced cations, maintaining the electrostatic attraction throughout.

In ionic crystals, applying a force aligns like charges, causing electrostatic repulsion and shattering. In metals, no such repulsion occurs because only positive cations are present in the lattice and the electron sea is non-directional.

The answer that mentions cation layers sliding, the delocalized electron sea, and non-directional bonding is correct.

This question tests the explanation of malleability using metallic bonding concepts — specifically non-directional bonding and the electron sea.

Metallic bonds are not necessarily weak — malleability arises from their non-directional nature, not their weakness. Iron has relatively strong metallic bonds yet is still malleable.

Localized electron pairs describe covalent bonding, not metallic bonding. In metals, electrons are delocalized throughout the structure, not located between specific atom pairs.

Iron does not have an ionic lattice with alternating charges. The description of 'like charges repelling to prevent shattering' is inaccurate — in ionic crystals, like-charge alignment actually causes shattering.

The correct answer correctly identifies cation layer sliding, non-directional bonding, and the delocalized electron sea maintaining attraction — all hallmarks of the metallic bonding explanation for malleability.