14
The elements of
Groups IB and MB
I (COPPER), SILVER, GOLD
In Mendeleefs periodic table, these three elements appeared to-
gether in Group IB, alongside the alkali metals (Group IA). We
have already considered copper, as a member of the first transition
series. Silver and gold show some resemblances to copper; all three
elements exhibit an oxidation state of +1; and all three metals
have rather similar physical properties (Table 14.1). All three metals
are difficult to convert to cations, since they have high ionisation
energies and heats of atomisation; they are therefore resistant to
attack by aqueous acids or alkalis (increasing resistance from copper
to gold); and all three have been used for making coins—hence
they are often called collectively the coinage metals.SILVER
THE METAL
Silver is formed in nature as argentile* Ag 2 S and horn silver. AgCl.
The extraction of silver depends upon the fact that it very readily
forms a dicyanoargentate(I) complex, [Ag(CN) 2 ]~ (linear), and
treatment of a silver ore with aqueous cyanide ion CN ~ extracts
the silver as this complex. The silver is then displaced from the
complex by zinc:
2[Ag(CN) 2 ]- + Zn -> 4CN- + Zn2+ + 2Ag(Zinc forms only an unstable complex with the cyanide ion.)
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