Donor atoms and oxidation states

You will write two functions that work with a table of ligands. One finds the coordination number of a complex. The other finds the oxidation state of the metal. You will also pick out the chelating ligands.

The idea. The coordination number is the number of donor atoms bonded to the metal. The oxidation state is the charge on the complex minus the charge from all the ligands.

Your tasks.

1. Complete coordination_number(content) so that it returns the number of donor atoms.
2. Complete oxidation_state(charge, content) so that it returns the oxidation state of the metal.
3. Set chelating to the list of ligands that have more than one donor atom, in the order of the table.