Thallium is a chemical element; it has symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861, in residues of sulfuric acid production. Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, from Greek θαλλός, thallós, meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862; Lamy by electrolysis, and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by zinc at the international exhibition, which opened on 1 May that year.
In chemistry, azide is a linear, polyatomic anion with the formula N−3 and structure −N=N+=N−. It is the conjugate base of hydrazoic acid HN3. Organic azides are organic compounds with the formula RN3, containing the azide functional group. The dominant application of azides is as a propellant in air bags.
In chemistry, a nitride is an inorganic compound of nitrogen. The "nitride" anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitrides have a found applications, such as wear-resistant coatings (e.g., titanium nitride, TiN), hard ceramic materials (e.g., silicon nitride, Si3N4), and semiconductors (e.g., gallium nitride, GaN). The development of GaN-based light emitting diodes was recognized by the 2014 Nobel Prize in Physics. Metal nitrido complexes are also common.
Potassium cyanate is an inorganic compound with the formula KOCN. It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was 20,000 tons in 2006.
Thallium(I) oxide is the inorganic compound of thallium and oxygen with the formula Tl2O in which thallium is in its +1 oxidation state. It is black and produces a basic yellow solution of thallium(I) hydroxide (TlOH) when dissolved in water. It is formed by heating solid TlOH or Tl2CO3 in the absence of air. Thallium oxide is used to make special high refractive index glass. Thallium oxide is a component of several high temperature superconductors. Thallium(I) oxide reacts with acids to make thallium(I) salts.
Thallium(I) chloride, also known as thallous chloride, is a chemical compound with the formula TlCl. This colourless salt is an intermediate in the isolation of thallium from its ores. Typically, an acidic solution of thallium(I) sulfate is treated with hydrochloric acid to precipitate insoluble thallium(I) chloride. This solid crystallizes in the caesium chloride motif.
Thallium(I) iodide is a chemical compound with the formula TlI. It is unusual in being one of the few water-insoluble metal iodides, along with AgI, CuI, SnI2, SnI4, PbI2 and HgI2.
The thallium halides include monohalides, where thallium has oxidation state +1, trihalides in which thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. These materials find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 μm), whereas zinc selenide is opaque by 21.5 μm, and ZnSe optics are generally only usable to 650 cm−1 (15 μm).
Thallium triiodide is a chemical compound of thallium and iodine with formula TlI3. Unlike the other thallium trihalides, which contain thallium(III), TlI3 is a thallium(I) salt and contains the triiodide ion, I−
3.
Explosophores are functional groups in organic chemistry that give organic compounds explosive properties.
Ammonium azide is the chemical compound with the formula [NH4]N3, being the salt of ammonia and hydrazoic acid. Like other inorganic azides, this colourless crystalline salt is a powerful explosive, although it has a remarkably low sensitivity. [NH4]N3 is physiologically active and inhalation of small amounts causes headaches and palpitations. It was first obtained by Theodor Curtius in 1890, along with other azides.
Potassium azide is the inorganic compound having the formula KN3. It is a white, water-soluble salt. It is used as a reagent in the laboratory.
Barium azide is an inorganic azide with the formula Ba(N3)2. It is a barium salt of hydrazoic acid. Like most azides, it is explosive. It is less sensitive to mechanical shock than lead azide.
Fluorine azide or triazadienyl fluoride is a yellow green gas composed of nitrogen and fluorine with formula FN3. Its properties resemble those of ClN3, BrN3, and IN3. The bond between the fluorine atom and the nitrogen is very weak, leading to this substance being very unstable and prone to explosion. Calculations show the F–N–N angle to be around 102° with a straight line of 3 nitrogen atoms.
Rubidium azide is an inorganic compound with the formula RbN3. It is the rubidium salt of the hydrazoic acid HN3. Like most azides, it is explosive.
Zinc azideZn(N3)2 is an inorganic compound composed of zinc cations (Zn2+) and azide anions (N−3). It is a white, explosive solid that can be prepared by the protonolysis of diethylzinc with hydrazoic acid:
Caesium azide or cesium azide is an inorganic compound of caesium and nitrogen. It is a salt of azide with the formula CsN3.
Transition metal azide complexes are coordination complexes containing one or more azide (N3−) ligands.
Homoleptic azido compounds are chemical compounds in which the only anion or ligand is the azide group, -N3. The breadth of homoleptic azide compounds spans nearly the entire periodic table. With rare exceptions azido compounds are highly shock sensitive and need to be handled with the upmost caution. Binary azide compounds can take on several different structures including discrete compounds, or one- two, and three-dimensional nets, leading some to dub them as "polyazides". Reactivity studies of azide compounds are relatively limited due to how sensitive they can be. The sensitivity of these compounds tends to be correlated with the amount of ionic or covalent character the azide-element bond has, with ionic character being far more stable than covalent character. Therefore, compounds such as silver or sodium azide – which have strong ionic character – tend to possess more synthetic utility than their covalent counterparts. A few other notable exceptions include polymeric networks which possess unique magnetic properties, group 13 azides which unlike most other azides decompose to nitride compounds (important materials for semiconductors), other limited uses as synthetic reagents for the transfer for azide groups, or interest in high energy density materials.
