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

1 Answer
anor277
Jan 12, 2017

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.

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