Competency #7
Answer and Explanation
The correct answer is A.
The compound FeCl2 contains Fe2+ and Cl- ions (with twice as many of the latter).
Based on chlorine's position in the periodic table, we know neutral Cl has 7 electrons in its outer shell. Chlorine tends to gains 1 electron to achieve a more stable electron configuration. In doing so, a Cl1- ion is formed.
Iron (Fe) is a transition metal. Based solely on the information in the periodic table, we cannot predict what ion iron will form. However, we can determine the ion of Fe that is contained in FeCl2. For any neutral compound, the overall charge must be zero. We can therefore write the following expression regarding the charge:
Total charge on FeCl2 = charge on Fe + charge on Cl + charge on Cl
0 = charge on Fe + -1 + -1
The only way the above expression can be true is if the charge on Fe is +2. Thus, the compound FeCl2 contains Fe2+ and Cl- ions.