Which sequence is correct regarding the first ionisation potential of coinage metals ?

Options

A. `Cu gt Ag gt Au`
B. `Cu lt Ag lt Au`
C. `Cu gt Ag lt Au`
D. `Ag gt Cu gt Au`

Answer

C

Explanation

In case of transition elements, `IE_(1)` first decreases from `3d` series to `4d` series (i.e. `Cu gt Ag`), due to increase in size from `Cu` to `Ag`.
Then `IE_(1)` increases from `4d` series to `5d` series (i.e., `Au gt Ag`) due to imperfect screening effect of `4f`-orbital in `Au`.
Thus `IE_(1)` of `Cu gt Ag lt Au`.