Answer: C
Note that all the ions have 10 electrons; that is, they are all isoelectronic with neon. Because
they all have the same number of electrons, the only factor that will determine their size will be
the nuclear charge — the greater the nuclear charge, the smaller the radius. Therefore, magne-
sium, with a nuclear charge of +2, has the smallest radius among these ions.
- Which of the following is the correct Lewis structure for the ionic compound Ca(ClO 2 ) 2?
A.B.C.D.E.Answer: C
- The compound expected when chlorine reacts with aluminum is
A. Al 2 Cl 3
B. Al 3 Cl 2
C. AlCl 3
D. Al 3 Cl
E. AlCl 2Answer: C
The compound is ionic — a metal (Al) bonded to a nonmetal (Cl). All ionic compounds are
solids at room temperature and pressure. Aluminum has 13 electrons. As an ion, it will lose 3
electrons to become isoelectronic with neon. Thus the aluminum ion will have the electronic
configuration ls^22 s^22 p^6.
Chlorine as a free element is diatomic (Cl 2 ); however, as an ion, it will gain one electron to
become isoelectronic with argon. The electronic configuration of the chloride ion is
1 s^22 s^22 p^63 s^23 p^6. The compound thus formed, aluminum chloride, has the formula AlCl 3.
O
CaO
O Cl OClOOCl CaOOClOOCl Ca^2 +−
OOCl−Cl O O Ca O O ClCl O O Ca^2 + O O ClPart II: Specific Topics