There is a solubility chart in my college chemistry class text for "Solubility of Ionic compounds in water". I have copied and pasted image of chart below. I was surprised to find a dozen ionic compounds marked "--" meaning "no data".
Among the entries marked "no data" are
and carbonate, chromate, and nitrate for Sn2+
It's hard to believe there is no solubility data on said ionic compounds. They should be either soluble, insoluble, slightly soluble, or an impossible compound. I asked my professor, and he said most of said compounds are too unstable to get reliable solubility data. In other words, the said cations and anions would not form a stable ionic compound long enough to test solubility. He also said it might not be the case for all the "--" no data compounds. Which of the said "no data" compounds are impossible compounds as distinguished from possible stable ionic compounds for which there is really no solubility data?