Assertion: Both [Cr(H2O)6]2+ and [Fe(H2O)6]2+ have same magnetic moment.
Reason: Number of unpaired electrons in Cr2+ and Fe2+ are same.
Answer & explanation
Correct answer: option 1
In [Cr(H2O)6]2+
x + 6(0) = 2
x = 2
24Cr : [Ar]4s13d5
Cr2+ = [Ar]3d4 (4 unpaired electrons)
In [Fe(H2O)6]2+
x + 6(0) = 2
x = 2
26Fe : [Ar]4s23d6
Fe2+ : [Ar]3d6 ( 4 unpaired electrons)
Both contains same number of unpaired electrons, hence their magnetic moment will be same.
Magnetic moment, u = \(\sqrt {n(n+2)}\) where n is the number of unpaired electrons.