Which of the following compounds is colorless?

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?

What are the different possible oxidation states exhibited by scandium $(Sc)$?

Which of the following ions is paramagnetic?

Identify the pair of elements in which the number of electrons in the $(n-1)$ shell is the same.

The first transition element is