The following statements discuss some coordination compounds. For each
coordination compound, give the complex ion and the counterions, the electron
configuration of the transition metal, and the geometry of the complex ion.
a. \(\mathrm{CoCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) is a compound used in
novelty devices that predict rain.
b. During the developing process of black-and-white film, silver bromide is
removed from photographic film by the fixer. The major component of the fixer
is sodium thiosul-fate. The equation for the reaction is:
$$\operatorname{AgBr}(s)+2 \mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}(a q)
\longrightarrow \\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad
\mathrm{Na}_{3}\left[\mathrm{Ag}\left(\mathrm{S}_{2}
\mathrm{O}_{3}\right)_{2}\right](a q)+\mathrm{NaBr}(a q)$$
c. In the production of printed circuit boards for the electronics industry, a
thin layer of copper is laminated onto an insulating plastic board. Next, a
circuit pattern made of a chemically resistant polymer is printed on the
board. The unwanted copper is removed by chemical etching, and the protective
polymer is finally removed by solvents. One etching reaction is:
$$\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}(a q)+4
\mathrm{NH}_{3}(a q)+\mathrm{Cu}(s) \longrightarrow \\\
\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad
2 \mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}(a q)$$
Assume these copper complex ions have tetrahedral geometry.
