The experimentally observed magnetic moment value, which match well with the spin-only values for the pair of aqueous ions is(Atomic number: $\mathrm{Cr}=24$, $\mathrm{Co}=27$, $\mathrm{Gd}=64$, $\mathrm{Tb}=65$, $\mathrm{Dy}=66$ and $\mathrm{Lu}=71$)
(a)Cr(III) and Gd(III)
(b)Co(II) and Gd(III)
Answer
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