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Classification of Elements and Periodicity in Properties
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23/08/2021 1:04 pm
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What is the order of ionisation energies of the coinage metal
(a) Cu > Ag < Au
(b) Cu > Ag > Au
(c) Cu < Ag < Au
(d) Au > Ag < Cu
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23/08/2021 1:10 pm
Correct answer: (a) Cu > Ag < Au
Explanation:
Cu = 3d10 4s1, Ag = 4d10 5s1, Au = 4f14 5d10 6s1
In all the above given cases, unpaired s-electron has 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, IE1 of Cu > IE1 of Ag.
However, in case of Au, due to imperfect screening effect of 14 e– s of 4f orbitals, the nuclear charge increases and therefore 5s e– of Au is more tightly held.
Thus, the order of IE1 is Cu > Ag < Au.