Answer:
a. AlCl is incorrect because Al has a +3 charge while Cl only has a -1 charge. The correct formula would be AlCl₃. This balances the charges.
b. Na₃SO₄ is incorrect because Na has a charge of +1 and there are three of them so its +3 and SO₄ has a charge of -2. The correct formula would be Na₂SO₄. This balances the charges.
c. BaOH₂ is incorrect because the polyatomic ion OH would not be written that way. It would be written like this Ba(OH)₂. Writing it like BaOH₂ gives the impression that instead of having 2 OH it has 2 H and 1 O.
d. Fe₂O is incorrect because Fe either has a +2 charge or +3 charge while O has a -2 charge. Possible correct answers could be FeO (iron (II) oxide) or Fe₂O₃ (iron (III) oxide).
