Thallium is a silvery white metal that tends to react with air when exposed to it. Two scientists, William Crookes, an English physicist, and Claude-Auguste Lamy, a French chemist, discovered thallium independently of each other in 1861. Thallium was named after the Greek word thallos, meaning ‘a green shoot’ or ‘a tree twig’. Thallium salts are used in rat and insect poisons. The element plays a significant role in nuclear medicine. The atomic number of thallium is 81, and its atomic symbol is Tl.
Lead is a heavy metal which is denser than many common metals. It is an incredibly useful metal, but it is also toxic to humans. Lead is widely used in a variety of products, including cosmetics, paint and gasoline. The chemical symbol for lead is Pb, which comes from the Latin word ‘plumbum’, meaning plumbing or waterworks. It has the atomic number 82.
Bismuth is a shiny brownish-silver metal. It is represented as Bi, and has the atomic number 83. Bismuth has been in use since ancient times, and was previously confused with both lead and tin. While no single person is credited with its discovery, it wasn’t until 1753 that Claude Geoffroy, a French chemist, discovered that it was a separate element.
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