Calcium Calcium Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
Calcium chlorate complicated by calcium hydroxide depositing on the cathode, preventing the flow of current. When concentrated solutions of calcium chlorate and potassium chloride are combined, potassium chlorate precipitates: This is the second step of the Liebig process for the manufacture of potassium chlorate. Solutions of calcium chlorate react with solutions of alkali carbonates to give a precipitate of calcium carbonate and the alkali chlorate in solution: On strong heating, calcium chlorate decomposes to give oxygen and calcium chloride: Cold, dilute solutions of calcium chlorate and sulfuric acid react to give a precipitate of calcium sulfate and chloric acid in solution: Contact