All ionic radii of the element as a dict of
        {oxidation state: ionic radii}. Radii are given in ang.

def ionic_radii(self):
        """
        All ionic radii of the element as a dict of
        {oxidation state: ionic radii}. Radii are given in ang.
        """
        if "Ionic radii" in self._data:
            return {int(k): v for k, v in self._data["Ionic radii"].items()}
        else:
            return {}