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
What Is the What What Is the What What Is the What: The Autobiography of Valentino Achak Deng is a 2006 novel written by Dave Eggers. It is based on the life of Valentino Achak Deng, a Sudanese child refugee who immigrated to the United States under the Lost Boys of Sudan program. It was a finalist for the National Book Award. As a boy, Achak is separated from his family during the Second Sudanese Civil War when the Arab militia, referred to as "murahaleen" (which is Arabic for the deported), wipes out his Dinka village, Marial Bai. During the assault, he loses sight