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
Ultrasonic soldering different process than ultrasonic welding. Ultrasonic welding uses ultrasonic energy to join parts without adding any kind of filler material while ordinary soldering uses external heating to melt filler metal materials, namely solders, to form a joint. Ultrasonic soldering can be done with either a specialized soldering iron or a specialized solder pot. In either case the process can be automated for large-scale production or can be done by hand for prototyping or repair work. Initially, U/S soldering was aimed at joining aluminum and other metals; however, with the emergence of active solders, a much wider range of metals, ceramics