Question

What salt should be formed by the interaction of aluminum metal and iodine?

Answer 1

This is a poor question. They ask you to predict a formula of `"AlI"_3`, `"aluminum triiodide"`.

Explanation:

`"Aluminum"` is a Group 13 metal; it is commonly oxidized to the `Al^(3+)` cation:

`AlrarrAl^(3+) + 3e^-`

On the other hand, iodine is a Group 17 non-metal. It is commonly reduced to give the iodide anion:

`1/2I_2 + e^(-) rarr I^-`

When aluminum and iodine make music together, i.e. combine in a redox reaction, 3 equiv of electrons of electrons are transfered:

`Al +3/2I_2rarr{Al^(3+)I_3^(-)}`. And `{Al^(3+)I_3^(-)}-=AlI_3`

We know that most matter is electrically neutral, and all I have done here is to draft enough iodide ions, formally anionic, to neutralize the charge of the `Al^(3+)` cation.