JEE Main & Advanced Chemistry Classification of Elements and Periodicity in Properties / तत्त्वों का वर्गीकरण एवं गुणों में आवर्ति Question Bank Self Evaluation Test - Classification of Elements and Periodicity in Properties

  • question_answer
    What is the order of ionisation energies of the coinage metal

    A) \[Cu>Ag<Au\] 

    B) \[Cu>Ag>Au\]

    C) \[Cu<Ag<Au\]              

    D) \[Au>Ag<Cu\]

    Correct Answer: A

    Solution :

        
    [a]\[Cu=3{{d}^{10}}4{{s}^{1}},\,\,Ag=4{{d}^{10}}5{{s}^{1}},\,\,Au=4{{f}^{14}}5{{d}^{10}}6{{s}^{1}}\]
    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, IE, of \[Cu>I{{E}_{1}}\]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 \[5s\text{ }{{e}^{-}}\] of Au is more tightly held.         
    Thus, the order of \[I{{E}_{1}}\]is\[Cu>Ag<Au.\]


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