## Chemistry: Principles and Practice (3rd Edition)

The formula for potassium nitrate is KNO$_3$. The formula for ammonium carbonate is (NH$_4$)$_2$CO$_3$.
According to the periodic table, potassium is an alkali metal and has a valence of 1+. Nitrate, according to Table 2.2 on page 65 in our book, has the formula NO$_3$$^-. These elements combine in a 1:1 ratio to make potassium nitrate (KNO_3). Ammonium's formula is NH^+. Carbonate's formula, according to Table 2.2 on page 65 of our book, is CO_3$$^{2-}$. These elements combine in a 2:1 ratio, meaning there should be two ammonium ions for every carbonate ion. The formula for ammonium carbonate is (NH$_4$)$_2$CO$_3$.