Question

Which of the following complexes will exhibit maximum attraction to an applied magnetic field?

• A. \( [Zn(H_2O)_6]^{2+} \)
• B. \( [Co(H_2O)_6]^{2+} \)
• C. \( [Co(en)_3]^{3+} \)
• D. \( [Ni(H_2O)_6]^{2+} \)

Hint:

Magnetic properties depend on the number of unpaired electrons. The higher the unpaired electrons, the stronger the attraction to a magnetic field.

Answer 1

The Correct Option is B

Step 1: Assess Magnetic Behavior
Paramagnetic complexes are characterized by the presence of unpaired electrons.
An increased number of unpaired electrons correlates with a heightened attraction to a magnetic field.
Step 2: Evaluate Electron Configurations
\( Zn^{2+} \) (\( d^{10} \)) exhibits 0 unpaired electrons, classifying it as diamagnetic.
\( Co^{2+} \) (\( d^7 \)) possesses 3 unpaired electrons, indicating paramagnetism.
\( Co^{3+} \) (\( d^6 \), low spin) has 0 unpaired electrons, thus being diamagnetic.
\( Ni^{2+} \) (\( d^8 \)) contains 2 unpaired electrons, rendering it paramagnetic, though with a lower magnetic attraction than \( Co^{2+} \).
Conclusion: \( [Co(H_2O)_6]^{2+} \) demonstrates the strongest paramagnetism due to its 3 unpaired electrons.