Which one is false in the following statement:

Which one of the following ionic species will impart colour to an aqueous solution?

Which of the following types of metals forms the most efficient catalysts:

Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?

Gallium is in __________ state at room temperature.

Most of the radio active elements are present in:

Among the following metals, interatomic forces are probably the weakest in:

The Lanthanide contraction relates to:

Some compounds turn dark when exposed to light. They are, therefore, used in photography. A metal used for making such compounds is:

Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because ___________.