The number of unpaired electrons in Gadolinium $[Z = 64]$ is

The magnetic moment of $M^{x+}$ (atomic number $= 25$) is $\sqrt{15} \ BM$. The number of unpaired electrons and the value of $x$,respectively,are

Which of the following statements is not true for transition elements?

Which of the following represents the decreasing order of the second ionization enthalpy $(I.P_2)$?

The first transition element is

The calculated spin-only magnetic moment of $Cr^{2+}$ ion is......$B.M.$