Number of colourless lanthanoid ions among the following is . . . . .
$Eu^{3+}, Lu^{3+}, Nd^{3+}, La^{3+}, Sm^{3+}$

Fill in the blanks given below:
$(i)$ Neptunium and Plutonium are obtained from ............ .
$(ii)$ Lanthanoid series and Actinoid series are known as ............ .
$(iii)$ The main energy level of an atom is called ............ .
$(iv)$ Elements that possess both metallic and non-metallic properties are called ............ .

Which electronic configuration is common to all actinoid elements?

Which transuranic elements are naturally present in trace amounts in uranium ore $U_3O_8$?

The common oxidation state of the elements of the lanthanoid series is .....

Knowing that the chemistry of lanthanoids $(Ln)$ is dominated by its $+3$ oxidation state,which of the following statements is incorrect?