Make a model for the the ionic bonding of Al and Cl.

ClAl

Explanation:

* = electron

Cl (17) * * * * * * *

Al (13) * * *

If one of aluminum's electrons were added to chlorine to make a full shell, still have 2 left over. So you need another:

Cl * * * * * * * * (full)

Cl * * * * * * *

Al * *

Still have another left over. Aluminum needs to lose another one of its valence electrons to be able to have a full shell. So you take another chlorine:

Cl * * * * * * * * (full)

Cl * * * * * * * * (full)

Cl * * * * * * *

Al *

You will eventuate with 3Cl and 1Al, or ClAl. Modeled above:

it takes on an electronical energy