Question #66d23

2 Answers
Nov 16, 2017

That compound is actually an ionic compound, not an ion in and of itself.

#AlCl_4# tells us there are 4 chloride anions and one aluminum (IV) cation.

#Al^(4+)# has four #Cl^(-)# ionically bonded to it.

Nov 17, 2017

#AlCl_4^-# is a binary ionic compound with a tetrahedral geometry and a net molecular charge of -1.

Explanation:

Geometry Determination:
=> Bonded #e^-# pairs = 4
=> NonBonded #e^-#pairs (on central element) = 0
=> Total bonded #e^-#pairs in binary structure = 4
=> #AX_4# Geometry (VSEPR Theory)
=> Tetrahedral Geometry

Formal and Net Charge:
Formal Charge of Element in Compound (FC) ...

FC = Valence electrons - (Bonded electrons/2) - Nonbonded electrons)

FC = #V - B/2 - N#

Formal Charge per element:
FC(Cl) = #7-2/2-6# = #0#
FC(Al) = #3-8/2-0# = #-1#

Net Molecular Charge:
#Sigma("Formal" "Charges") = 4(Cl) + 1(Al)# = #4(0) + 1(-1)# = #-1#

https://en.wikipedia.org/wiki/Tetrachloroaluminate