. The ionisation energy of the coinage metals fall in the order

Cu > Ag < Au

Best Answer

Answer: In all the 3 cases an s-electron in the unpaired state is to be removed. In the case of Cu a 4s electron is to be removed which is closer to the nucleus than the  5s electron of Ag. So I.P. decreases from Cu to Ag. However from Ag to Au the 14 f electrons are added which provide very poor shielding  effect. The nuclear charge is  thus enhanced  and therefore the outer electron of Au  is more tightly held and so the IP is high.

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