= Solution
For comparable octahedral environments with the same donor set, the expected qualitative order is
$$
\boxed{\mathrm{Mn^{2+}<Fe^{2+}<Fe^{3+}<Mo^{3+}<Rh^{3+}<Pt^{4+}}.}
$$
Across comparable first-row ions, the increasing effective attraction and changing <metal>–ligand distances tend to increase <octahedral splitting>, giving Mn(II) below Fe(II). Raising the charge on the same <metal> gives Fe(III) above Fe(II), because the ligand interaction generally strengthens and <metal>–ligand distances contract. Moving from $3d$ to more radially extended $4d$ orbitals gives larger <metal>–ligand overlap, placing Mo(III) above Fe(III); Rh(III) lies further along the same $4d$ series and typically gives the larger splitting. The $5d$ ion Pt(IV) combines the heavier row with high charge and gives the largest splitting here.
\b[This is a matched-environment trend, not an intrinsic list of constants for bare ions.] Actual $\Delta$ also depends strongly on donor identity, geometry and distance. It would be meaningless to compare an unspecified weak-field tetrahedral compound with a strong-field octahedral compound solely through this ordering.
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