Which of the following does not contain silicon?

The electronic configurations of four elements are:
$(i) \; [Xe] \; 6s^1$
$(ii) \; [Xe] \; 4f^{14}5d^16s^2$
$(iii) \; [Ne] \; 3s^23p^5$
$(iv) \; [Ar] \; 3d^74s^2$
Which one of the following statements about these elements is not true?

Which one of the following belongs to the $3d-$ transition series?

Which of the following compounds is expected to be coloured?

Assertion : Transition metals show variable valency.
Reason : Transition metals have a large energy difference between the $ns^2$ and $(n-1)d$ electrons.

Which of the following ions is colourless in solution?