Science, Tech, Math › Science Solubility Rules of Ionic Solids Share Flipboard Email Print STUDIO BOX / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated November 19, 2019 This is a list of the solubility rules for ionic solids in water. Solubility is a result of an interaction between polar water molecules and the ions that make up a crystal. Two forces determine the extent to which the solution will occur: Force of Attraction Between H2O Molecules and the Ions of the Solid This force tends to bring ions into solution. If this is the predominant factor, then the compound may be highly soluble in water. Force of Attraction Between Oppositely Charged Ions This force tends to keep the ions in the solid state. When it is a major factor, then water solubility may be very low. However, it is not easy to estimate the relative magnitudes of these two forces or to quantitatively predict water solubilities of electrolytes. Therefore, it is easier to refer to a set of generalizations, sometimes called "solubility rules," that is based upon experimentation. It's a good idea to memorize the information in this table. Solubility Rules All salts of the group I elements (alkali metals = Na, Li, K, Cs, Rb) are soluble. NO3: All nitrates are soluble. Chlorate (ClO3-), perchlorate (ClO4-), and acetate (CH3COO- or C2H3O2-, abbreviated as Oac-) salts are soluble. Cl, Br, I: All chlorides, bromides, and iodides are soluble except those of silver, mercury, and lead (e.g., AgCl, Hg2Cl2, and PbCl2). SO42: Most sulfates are soluble. Exceptions include BaSO4, PbSO4, and SrSO4. CO32: All carbonates are insoluble except NH4+ and those of the Group 1 elements. OH: All hydroxides are insoluble except those of the Group 1 elements, Ba(OH)2, and Sr(OH)2. Ca(OH)2 is slightly soluble. S2: All sulfides are insoluble except those of the Group 1 and Group 2 elements and NH4+.