Question

how do you predict precipitates of ionic reaction?

Answer 1

The elements of a period 4 starts a new cycle of properties after the element Argon, because their electrons differ in numbers. A period 4 element is one of the chemical elements in the fourth row (or period) of the periodic table of the elements.

Answer 2

There is a whole table used to predict if aqueous solutions will form a precipitate as a product. http://intro.chem.okstate.edu/html/SCSIMG/SCH1650.gif

Answer 3

You can't predict unless you have the solubility product of the solution.