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Why does sodium chloride form a crystal lattice instead of separate molecules?

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representations of molecular structure — molecule Several methods of representing a molecule's structure. In Lewis structures, element symbols represent atoms, and dots represent electrons surrounding them. A pair of shared electrons (covalent bond) may also be shown as a single dash. The ball-and-stick model better illustrates the spatial arrangement of the atoms. For aromatic compounds, the Kekulé structure is common, in which each bond is represented by a dash, carbon atoms are implied where two or more lines meet, and hydrogen atoms are usually omitted. Bond-line formulas, similar to the Kekulé structure, are often used for complex nonaromatic organic compounds. Sugars are often drawn as Fischer projections, in which the carbon “backbone” is drawn as a straight vertical line, with carbon atoms implied where horizontal lines intersect the vertical one.

Sodium chloride does not form separate molecules because it is an ionic compound held together by the electrostatic attraction between oppositely charged ions, rather than by covalent bonds that typically define discrete molecules.12

When sodium reacts with chlorine, an electron is transferred from the sodium atom to the chlorine atom, creating a cation (Na⁺) and an anion (Cl⁻). These ions do not exist as isolated pairs; instead, they arrange themselves into a crystal lattice where every positive ion is surrounded by negative ions and vice versa.123

This structure is energetically favorable because the packing of ions allows for strong, widespread electrostatic interactions among many ions of opposite charge. The release of energy during this formation, known as lattice energy, is significant enough to make the solid crystal more stable than the individual elements. Consequently, the substance exists as a continuous, repeating array of ions rather than as independent molecular units.314