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
International breastfeeding symbol public places. These signs need to be designed carefully because they need to be understood at a glance by most people without written descriptions explaining what they mean. The International Breastfeeding Symbol was created specifically to address the perceived problem of not having a universally accepted and understood symbol for breastfeeding available in public places. The modern iconography representing infancy usually involves artificial feeding or soothing objects, like a nurser bottle icon or pacifier symbol. Nursing rooms traditionally use a baby bottle symbol to designate what they are instead of a symbol of a mother nursing a child. The International