The number of $d$-electrons in $Cr^{3+}$ ion $(Z=24)$ is

The electronic configurations of four elements are:
$(i) \; [Xe] \; 6s^1$
$(ii) \; [Xe] \; 4f^{14}5d^16s^2$
$(iii) \; [Ne] \; 3s^23p^5$
$(iv) \; [Ar] \; 3d^74s^2$
Which one of the following statements about these elements is not true?

$Mn^{2+}$ compounds are more stable than $Fe^{2+}$ compounds towards oxidation to their $+3$ state,because

Which metal is used to make alloy steel for armour plates,safes and helmets?

Gadolinium has a low value of third ionisation enthalpy because of $......$

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