where n is the number of unpaired electrons. The spin-only formula is a good first approximation for high-spin complexes of first-row transition metals.Figgis&Lewis, p. 406 {|class="wikitable" style="text-align:center" !Ion!!Number of unpairedelectrons!!Spin-only moment /μB!!observedmoment /μB |- |Ti3+ ||1||1.73||1.73 |- |V4+||1 ||  ||1.68–1.78 |- |Cu2+ ||1 ||  ||1.70–2.20 |- |V3+||2||2.83||2.75–2.85 |- |Ni2+||2||  ||2.8–3.5 |- |V2+ ||3||3.87||3.80–3.90 |- |Cr3+ ||3||  ||3.70–3.90 |- |Co2+ ||3||  ||4.3–5.0 |- |Mn4+ ||3||  ||3.80–4.0 |- |Cr2+ ||4||4.90 ||4.75–4.90 |- |Fe2+ ||4 ||  ||5.1–5.7 |- |Mn2+ ||5||5.92 ||5.65–6.10 |- |Fe3+ ||5||  ||5.7–6.0 |} The small deviations from the spin-only formula may result from the neglect of orbital angular momentum or of spin-orbit coupling. For example, tetrahedral d3, d4, d8 and d9 complexes tend to show larger deviations from the spin-only formula than octahedral complexes of the same ion, because "quenching" of the orbital contribution is less effective in the tetrahedral case.Figgis&Lewis, Section 3, "Orbital contribution"
where n is the number of unpaired electrons. The spin-only formula is a good first approximation for high-spin complexes of first-row transition metals.Figgis&Lewis, p. 406 {|class="wikitable" style="text-align:center" !Ion!!Number of unpairedelectrons!!Spin-only moment /μB!!observedmoment /μB |- |Ti3+ ||1||1.73||1.73 |- |V4+||1 || 1.73 ||1.68–1.78 |- |Cu2+ ||1 || 1.73 ||1.70–2.20 |- |V3+||2||2.83||2.75–2.85 |- |Ni2+||2|| 2.83 ||2.8–3.5 |- |V2+ ||3||3.87||3.80–3.90 |- |Cr3+ ||3|| 3.87 ||3.70–3.90 |- |Co2+ ||3|| 3.87 ||4.3–5.0 |- |Mn4+ ||3|| 3.87 ||3.80–4.0 |- |Cr2+ ||4||4.90 ||4.75–4.90 |- |Fe2+ ||4 || 4.90 ||5.1–5.7 |- |Mn2+ ||5||5.92 ||5.65–6.10 |- |Fe3+ ||5|| 5.92 ||5.7–6.0 |} The small deviations from the spin-only formula may result from the neglect of orbital angular momentum or of spin-orbit coupling. For example, tetrahedral d3, d4, d8 and d9 complexes tend to show larger deviations from the spin-only formula than octahedral complexes of the same ion, because "quenching" of the orbital contribution is less effective in the tetrahedral case.Figgis&Lewis, Section 3, "Orbital contribution"
A
1.73
A
1.73
A
2.83
A
3.87
A
3.87
A
3.87
A
4.90
A
5.92