Co Còbalt 27 58.933195 9 4 d 27 1495.0 2870.0 [Ar] 3d7 4s2 2 8 15 2 8.9 0.003% Gray Hexagonal 1.9 1.84 {"1":"760.4","2":"1648","3":"3232","4":"4950","5":"7670","6":"9840","7":"12440","8":"15230","9":"17959","10":"26570","11":"29400","12":"32400","13":"36600","14":"39700","15":"42800","16":"49396","17":"52737","18":"134810","19":"145170","20":"154700","21":"167400","22":"178100","23":"189300","24":"204500","25":"214100","26":"920870","27":"966023"} 761 63.7 126 +2,3 1.25 6.7 16.19 373.3 0.421 100.0 0 Solid, Ferromagnetic, Conductor, TransitionMetal, Metal, Stable, Natural KO-bolt Hard, ductile, lustrous bluish-gray metal. Exists in the earth's curst in cocentrations of about 25 ppm. It has remarkable magnetic properties. Used in many hard alloys; for magnets, ceramics and special glasses. Remains hard up to 982°C. Radioactive cobalt-60 is used in cancer therapy. Occurs in compounds with arsenic, oxygen and sulfur as in cobaltine (CoAsS) and linneite (Co3S4). Pure cobalt is obtained as a byproduct of refining nickel, copper and iron. V6ljxByu9ng Cobalt

Around 1630, chlorine was recognized as a gas by the Belgian chemist and physician Jan Baptist van Helmont.

Elemental chlorine was first prepared and studied in 1774 by Swedish chemist Carl Wilhelm Scheele.

By 1810, the scientific consensus was that chlorine was actually a compound that contained oxygen.

In 1811, Sir Humphry Davy concluded the new gas was in fact a new element. From the Greek word chloro, greenish yellow 27 1735 Georg Brandt Sweden From the German word "kobald" meaning "goblin" or evil spirit

Elemental chlorine at high concentrations is extremely dangerous and poisonous

Tree frogs have a chlorine compound in their skin that is a very powerful pain killer

Chlorine is used for producing safe drinking water.

It is also extensively used in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, food, solvents, paints, plastics, and many other consumer products.

Chlorinated compounds are used mostly for sanitation, pulp bleaching, disinfectants, and textile processing.