In 2021, we reported the first instance of thorium–thorium bonding in a crystalline cluster. This compound has sparked significant interest due to its hotly debated electronic structure, which is predicted by density functional theory to exhibit valence-delocalisation of two 6d electrons over three Th metal centres, leading to an antiferromagnetic 6d2 ground state. Ab initio RIXS calculations predict low energy transfer (<5 eV) 6d-6d and spin excitations, which will serve as direct experimental evidence of the electronic structure. We propose high energy resolution 2p6d RIXS at ID20 to test density functional theory predictions and settle the ongoing contention concerning the electronic structure of this molecule. By examining molecular Th analogues, we aim to demonstrate 2p6d RIXS as a reliable probe of valence d electron count in lanthanides and actinides.