I'm struggling with identifying the compounds described in the question that I have attached in the file below.
My thinking behind how to do this question is that compound C must involve a lanthanide which can reach a stable +2 oxidation state, meaning that the lanthanoid metal A is either Eu, Yb, Sm or Tm.
I also know that Eu, Yb and Sm can participate in comproportionation reactions with their oxides of the form Ln2O3 (where Ln is the lanthanoid metal), and out of these three Ln2O3 oxides, Yb2O3 is colourless and features a dipole moment. Therefore my suggested answers to the question are:
But then I don't understand the colours for compounds C and D. I know for YbCl3 this is colourless because it doesn't absorb in the visible region, but then I would expect YbO to also be colourless due to the lack of f-f transitions.
Please can I have some help with identifying these compounds, and if I got them right why YbO seems to have a green colour?