Question

Considering $H_{2}O$ as weak field ligand, the number of unpaired electrons in $\left[Mn\right(H_{2}O{)}_6{]}^{2+}$ will be:
(Atomic number of Mn=25):

• A. three
• B. five
• C. two
• D. four

Answer 1

The correct option is B five

$H_{2}O$ is a weak field ligand.
In $\left[Mn\right(H_{2}O{)}_6{]}^{2+},Mn$ is present as $M{n}^{2+}$ so its electronic configuration will be
$1s^2,2s^{2}2p^6,3s^{2}3p^6,3d^5$In $Mn(H_{2}O{)}_6{]}^{2+}$ the co-ordination number of $Mn$ is six, but in presence of weak ligand field, there will be no pairing of electrons in 3d. So it will from high spin complex due to presence of five unpaired electron.
In $\left[Mn\right(H_{2}O{)}_6{]}^{2+}$