Short answerQuestion 1 · Recall
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By the end you can describe the structure of a simple molecular solid — iodine, buckminsterfullerene or ice — and explain what holds it together.
A simple molecular solid is built from small, separate molecules.
Inside each molecule, the atoms are joined by strong covalent bonds. Between one molecule and the next, the forces are weak intermolecular forces.
That split — strong within, weak between — explains almost everything about these solids.
Simple molecular structure
A simple molecular solid is a lattice of separate molecules held together by weak intermolecular forces (for example van der Waals' forces or hydrogen bonds).
| substance | what the molecules are | what holds the solid together |
|---|---|---|
| iodine, | pairs of iodine atoms | van der Waals' forces between molecules |
| buckminsterfullerene, | 60 carbon atoms in a ball-shaped molecule | van der Waals' forces between the balls |
| ice | molecules | hydrogen bonds between water molecules |
Note the pattern: the covalent bonds never break when these solids melt — only the weak forces between molecules give way.
Picture strong velcro inside each marble-sized molecule and a whisper of static between marbles.
To melt the solid you only need to separate the marbles — the velcro stays fastened. That is why iodine melts and sublimes without ever breaking an I–I bond.
Where it breaks down: real intermolecular forces are electrical attractions, not sticky patches. But the "strong inside, weak outside" split is exact.