= Solution
The <isolobal analogy> compares fragments through their <frontier molecular orbitals>: their number, approximate energies, shapes, symmetries and <electron> occupancies should correspond. It does not require the fragments to have the same total number of <electrons> or the same constituent elements. If the orbitals available for forming new bonds correspond, analogous ways of joining the fragments become plausible.
For example, \b[$\mathrm{CH_3^{\bullet}}$ and $\mathrm{Mn(CO)_5^{\bullet}}$ are isolobal]. The <methyl radical> has one singly occupied approximately outward-pointing orbital; removing one <carbonyl ligand> from an <octahedral molecular geometry> leaves an analogous frontier orbital on the 17-electron $\mathrm{Mn(CO)_5}$ fragment. Joining two such fragments pairs the two <electrons>: the organic example is the C–C bond of <ethane>, and the organometallic example is the Mn–Mn bond of $\mathrm{Mn_2(CO)_{10}}$. The analogy predicts a bonding pattern, rather than equality of bond energies or reaction rates.<Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture) by Roald Hoffmann>[1982, discussion of the methyl and metal-carbonyl fragment analogy]{ref}
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