Thallium, chemical symbol Tl, atomic number 8 1, is a group Ⅲ A element in the sixth period of the periodic table of elements, and its content is very low in the natural environment, so it is an associated element. Thallium dissolves slowly in hydrochloric acid and dilute sulfuric acid and rapidly in nitric acid. Its main compounds are oxides, sulfides, halides and sulfates. Thallium salts are generally colorless and odorless crystals, which form thallium compounds after being dissolved in water.

thallium

Like lead, thallium is soft, with low melting point and low tensile strength. The surface of newly cut thallium has metallic luster, which quickly darkens and turns blue-gray in room temperature air. Exposure to air for a long time will form a thick unprotected oxide layer. Thallium has three kinds of metamorphosis, hexagonal close-packed crystal system below 503K, body-centered cubic crystal system above 503K and face-centered cubic crystal system under high pressure.

Thallium reacts rapidly with wet air or oxygen-containing water to form TlOH. Thallium reacts easily with halogen at room temperature, but it can react with sulfur and phosphorus at high temperature, but it does not react with hydrogen, nitrogen, ammonia or dry carbon dioxide. Thallium dissolves slowly in sulfuric acid and hardly in hydrochloric acid and hydrofluoric acid, because insoluble salts are formed on the surface. Thallium is insoluble in alkali solution, but easily forms water-soluble thallium nitrate with nitric acid.

Refer to the above content: Baidu Encyclopedia-Thallium