Multiple choiceQuestion 1 · Apply
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By the end you can predict and explain electrical conductivity and solubility from a substance's structure and bonding.
A substance conducts electricity only if it contains charged particles that are free to move.
So the checklist is simple: are there mobile ions, or mobile (delocalised) electrons?
| structure | solid | molten | aqueous (in water) | who carries the charge |
|---|---|---|---|---|
| giant metallic (copper) | conducts | conducts | — (insoluble) | delocalised electrons |
| giant ionic (NaCl) | does not conduct | conducts | conducts (if soluble) | ions, free when not locked in the lattice |
| giant molecular — graphite | conducts (along layers) | — (sublimes) | — (insoluble) | delocalised electrons in the layers |
| giant molecular — diamond, SiO₂ | does not conduct | — | — (insoluble) | none: all electrons locked in bonds |
| simple molecular (iodine, ice) | does not conduct | does not conduct | does not conduct | none: no ions, no delocalised electrons |
Ions in a solid lattice are pupils stuck to their seats — charges exist, but none can travel.
Melt or dissolve the lattice and the pupils are free to move around the room: now charge flows.
Delocalised electrons are pupils who are always roaming — metals and graphite conduct in every state.