Which of the following will not form an amalgam?

$E^{\circ}_{M^{3+} \mid M^{2+}} \text{ (in } V\text{) is highest for}$

Which element can have oxidation state from $4$ to $6$?

The highest oxidation state of manganese in fluoride is $+4$ $(MnF_4)$,but the highest oxidation state in oxides is $+7$ $(Mn_2O_7)$ because __

Fill in the blanks:
$(a)$ The only $Mn$ halide compound that shows an oxidation state of $+7$ is ........
$(b)$ The $E^{\ominus}_{M^{II}/M}$ value is maximum negative for ........ in the $3d$ series.
$(c)$ Between $Cr^{2+}$ and $Fe^{2+}$,the stronger reducing agent is ........

Which of the following is not amphoteric?