Question

The d-electron configurations of $Cr^{2+},Mn^{2+},Fe^{2+}$ and $Co^{2+}$ are $d^4, d^5, d^6$ and $d^7$ respectively. Which one of the following will exhibit the lowest paramagnetic behaviour? (Atomic no. $Cr=24, Mn=25, Fe=26, Co=27$).

• A. $[Co(H_2O)_6]^{2+}]$
• B. $[Cr(H_2O)_6]^{2+}]$
• C. $[Mn(H_2O)_6]^{2+}]$
• D. $[Fe(H_2O)_6]^{2+}]$

Answer 1

Answer: (A)

$[Co(H_2O)_6]^{2+}]$

Answer 2

$\therefore$ Since $Co^{2+}$ has lowest no. of unpaired electrons hence lowest paramagnetic behaviour is shown by $[Co(H_2O)_6]^{2+}$