As with many of the other rules, there are exceptions including barium, calcium, magnesium, sodium, potassium, and ammonium. Recognize that most sulfides are insoluble in water.For example: Na 2SO 4 is completely soluble, but CaSO 4 and BaSO 4 are not soluble.Sulfate salts containing these ions are insoluble. Exceptions to this rule include the following ions Ca +2, Ba +2, Pb +2, Ag +, Sr +2, and Hg +2. Most of the salt compounds containing SO 4 are soluble in water. Understand that most sulfate salts are soluble.For example: Compounds like CaCO 3, PbCrO 4, and Ag 3PO 4 are all insoluble while compounds like Na 3PO 4 and (NH 4) 2CO 3 are soluble.Exceptions to this rule include the Group 1A metals and NH 4 + compounds which are soluble. The chemical formulas for each of these are as follows: CO 3 (carbonates), CrO 4 (chromates), and PO 4 (phosphates). Know that most carbonates, chromates, and phosphates are insoluble.Note that PbCl 2, PbBr 2, and PbI 2 are soluble in HOT water.For example: AgCl and Hg 2Cl 2 are both insoluble.Compounds consisting of these nonmetals and ions are not soluble. Exceptions to this rule include silver, lead, and mercury. Group 17 nonmetals include chlorine (Cl -), bromine (Br -), and iodine (I -). Recognize that salts containing Group 17 nonmetals are generally soluble.
For example: Fe(OH) 3, Al(OH) 3, and Co(OH) 2 are insoluble, but LiOH and NaOH are soluble.The exception to this rule is that hydroxide salts formed with Group 1 elements are soluble because Group 1A elements are always soluble.
Some hydroxide salts are slightly soluble: hydroxides formed with Group 2 elements (Ca, Sr, and Ba).
They are the alkali metals and include Li, Na, K, Cs, and Rb. The first column of the table contains the Group 1A elements. The periodic table is organized into rows and columns called periods and groups, respectively. Recognize that salts containing Group 1A elements are soluble.