What is the general outer configuration of the coinage metals?
(a) $\mathrm{ns}^{2} \mathrm{np}^{6}$
(b) $(\mathrm{n}-1) \mathrm{d}^{9} \mathrm{~ns}^{2}$
(c) $(\mathrm{n}-1) \mathrm{d}^{10} \mathrm{~ns}^{1}$
(d) $(\mathrm{n}-1) \mathrm{d}^{10} \mathrm{~ns}^{2}$