The colour of an electrolyte solution depends on

State the reason for the stability of the $Gd^{3+}$ ion.

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:

The correct order of ionisation energy is:

The correct electronic configuration of the element $Au$ is

The element which shows only one oxidation state other than its elemental form is: