Why is the first ionisation enthalpy of $Cr$ lower than that of $Zn$?

Explain the exceptions in the general electronic configuration of $3d$-series elements.

The $3d-$ elements show variable oxidation states. What is the maximum oxidation state shown by the element $Mn$?

Number of paramagnetic ions among the following $d$- and $f$-block metal ions is . . . . . . . $Mn^{2+}$,$Cu^{2+}$,$Zn^{2+}$,$Yb^{2+}$,$Sc^{3+}$,$La^{3+}$,$Gd^{3+}$,$Lu^{3+}$,$Ti^{4+}$,$Ce^{4+}$. (Atomic number of $Mn = 25$,$Cu = 29$,$Zn = 30$,$Yb = 70$,$Sc = 21$,$La = 57$,$Gd = 64$,$Lu = 71$,$Ti = 22$,$Ce = 58$)

Write a brief note on the electronic configurations of the transition elements.

The number of $4f$ electrons in the ground state electronic configuration of $Gd^{2+}$ is ........ .
[Atomic number of $Gd=64$]