William Crookes first discovered thallium in 1861. It is a soft and bluish-white metal in color. It is symbolically written as Tl, and its atomic no. is 81. It looks very similar to lead, but has chemical resemblance to aluminum.
The name thallium is derived from the Greek word "thallios",which means a green twig. It is associated with a green twig because on burning, it creates a spectrum of light that has a thin green lining.
The soft texture allows thallium to be easily cut by a knife. It easily very reacts with H2O, air, and almost all the acids. But its reactive ability is not as volatile as that of the alkali metals.
The metal itself, as well as its various compounds are very toxic. Thallium poisoning was used for rodents, and also as insecticides, but this practice has now been discontinued. The U.S. Environmental Protection Agency (EPA) has created strict rules regarding the usage of thallium and its compounds.
It can enter the human body through injections, skin pores, and inhalation of harmful fumes and dust. Following are the other details of thallium.
The Element Thallium (TI)
- Element Classification: Metal
- Atomic Number: 81
- Atomic Weight: 204.3833
- Period Number: 6
- Group Number: 13
- Melting Point: 577 K
- Boiling Point: 1746 K
- Density: 11.8 gm/cubic cm
- State at Room Temperature: Solid
What are the Uses of Thallium
This element is not used anywhere, because the pure form reacts with oxygen and water vapors present in the atmosphere in a very volatile manner, and forms a black powdery substance.
Thallium is used in conjunction with other metals like sulfur and arsenic for the formation of low melting point glasses. They are similar to ordinary glasses, and are more durable and insoluble in H2O.
One of the most common uses of this element was rat and ant poisoning, which is now banned. Its compounds like thallium sulfide (TI2S), thallium bromide (TIBr), and thallium iodide (TII) are used in infrared radiation detecting devices. Thallium oxide is used in making high index refraction glasses and manufacturing photocells.
You can also find the incorporation of thallium for skin infection and ringworm treatment methods, though its use has been restricted because of its toxic nature. It plays a very important role as a catalyst for creating certain compounds. Medical equipment also uses thallium in the form of radioactive compounds in cardiovascular imaging.
This element is also used as a semiconductor materials for selenium rectifier. It has an excellent alloying property along with mercury for measuring low temperature. In a thallium stress test (a type of nuclear scanning test), this element is used for checking the blood flow in heart muscles.
The Earth's crust has approximately 0.7 ppm (parts per million) of thallium in it, which is an abundant amount. This element is obtained as a byproduct during the process of making zinc ores.
It can also be obtained from copper and lead ore, and also from the flue pipe of zinc, lead, and copper smelters in the form of dust. Canada, Europe, and the United States have rich reservoirs of thallium. According to the estimation made by the geologists, 17 million kilogram thallium is present worldwide.
Apart from this, nearly 630 million thallium can be extracted from coal. Even the ocean floor is made up of manganese nodules that have this element present in them, though extracting it is a pretty expensive affair.