Silver

Silver is a very ductile, malleable (slightly harder than gold), monovalent coinage metal, with a brilliant white metallic luster that can take a high degree of polish. It has the highest electrical conductivity of all metals, even higher than copper, but its greater cost has prevented it from being widely used in place of copper for electrical purposes. (Despite this, 13,540 tons were used in the electromagnets used for enriching uranium during World War II, mainly because of the wartime shortage of copper.) An exception to this is in radio-frequency engineering, particularly at VHF and higher frequencies, where silver plating to improve electrical conductivity of parts, including wires, is widely employed.

Silver plays no known natural biological role in humans, and possible health effects of silver are a disputed subject. Silver itself is not toxic, but most silver salts are, and some may be carcinogenic. Silver and compounds containing it (such as colloidal silver) can be absorbed into the circulatory system and become deposited in various body tissues, leading to argyria, which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Although this condition does not otherwise harm a person's health, it is disfiguring and usually permanent. Argyria is rare, and mild forms are sometimes mistaken for cyanosis.