Which of the following metal ions is diamagnetic?

Identify the order in which the spin-only magnetic moment (in $BM$) increases for the following four ions:
$(I) Fe^{2+}$
$(II) Ti^{2+}$
$(III) Cu^{2+}$
$(IV) V^{2+}$

Which element belongs to the $d-$block?

Which of the following groups of transition metals is known as coinage metals?

Variable valency is shown by

Number of unpaired electrons in $Mn^{2+}$ is