Although $Zr$ belongs to the $4d$ and $Hf$ belongs to the $5d$ transition series, it is quite difficult to separate them. Why?

The magnetic moment of a transition metal compound has been calculated to be $3.87 \ B.M.$ The metal ion is

Consider $|x|$ as the difference in oxidation states of Mn in the highest manganese fluoride and the highest manganese oxide. The ions with $|x|$ number of unpaired electrons from the following are: $A$. $Sc^{3+}$ $B$. $Zn^{2+}$ $C$. $V^{2+}$ $D$. $Fe^{2+}$ $E$. $Co^{2+}$ Choose the correct answer from the options given below:

Which of the following pairs of ions may exhibit the same colour?

What is the highest oxidation state of third row transition elements?

Which one of the following has the maximum number of unpaired electrons?