Which of the following is the heaviest metal?

Identify the correct decreasing order of densities of $d-$block elements.

Fill in the blanks:
$(a)$ The shielding effect of $d$-electrons is ......... effective than $p$-electrons.
$(b)$ $A$ decrease in exchange energy leads to a ......... in stability.
$(c)$ The maximum oxidation state of $Mn$ is ..........
$(d)$ The stability of $Mo(VI)$ and $W(VI)$ is found to be .......... than that of $Cr(VI)$.

In which of the $f$-block elements is the number of electrons in the $(n-2)f$ subshell zero?

Which of the following electronic configurations represents a transition element?

In the $3d$ series of the $d$-block elements,which element has the maximum atomic size?