Period 6 element period 6 other metals are incredibly toxic, such as thallium. Period 6 contains the last stable element, lead. All subsequent elements in the periodic table are radioactive. After bismuth, which has a half-life or more than 10 years, polonium, astatine, and radon are some of the shortest-lived and rarest elements known; less than a gram of astatine is estimated to exist on earth at any given time. Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes
Electrical contacts operation is logically inverted from Form A. An alternate notation for "Form B" is SPST-NC. "Form C" contacts ("change over" or "transfer" contacts) are composed of a normally closed contact pair and a normally open contact pair that are operated by the same device; there is a common electrical connection between a contact of each pair that results in only three connection terminals. These terminals are usually labelled as "normally open", "common", and "normally closed" ("NO-C-NC"). An alternate notation for "Form C" is SPDT. These contacts are quite frequently found in electrical switches and relays as the common contact element