Thallium Element Overview and Chemical Behavior

Thallium is a chemical element having symbol TI with an atomic number of 81, as found in the periodic table. It is not found freely in nature and is a grey post-transition metal. Thallium resembles tin when it's isolated but discolours when it is exposed to air. William Crookes and Claude-Auguste Lamy independently discovered Thallium in 1861. Approximately there are 81 electrons inside an atom of this element. The respective electronic configuration of Thallium is [Xe] 4f14 5d10 6s2 6p1. This element is not exclusively found or created naturally; rather, it can be created artificially by smelting lead and zinc. Thallium is also produced as a by-product while producing sulphuric acid. 

Here is a Summary of the Relevant Attributes of the Element Thallium

Uses of Thallium

Some of the uses of thallium include:

• Catalyst during organic reactions

• For producing optic laser and related equipment

• Radioisotopes and Mercury Lamps

• Used in Infra-Red Photocells

• It is also beneficial in detecting gamma radiation

• It is also used manufacturing glasses

• In ancient times, it was found helpful in killing ants and rats.

• Certain Thallium salts have been used for skin treatments; however, it has more side-effects than benefits because of its highly toxic nature.

Physical Properties of Thallium

Thallium is a malleable metal and looks like Lead (Atomic Number 82) in appearance. Some of its peculiar properties are as follows:

• It is very soft and melts easily. It can be cut through with a knife and will leave a mark when rubbed on a paper

• It is heavy and bluish-white in appearance

• On exhibition to air, it presents a metallic luster as well

• It is sufficiently abundant

• Its salts are soluble and usually toxic 

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Chemical Properties of Thallium

A few noteworthy chemical properties of Thallium are:

• Thallium has a +3 and +1 oxidation state. A +1 oxidation state is although much more stable and shows the chemistry of similarity to alkali metals

• Thallium reacts with air to create a grey oxide film and when it is heated to enormous amounts it leads to creation of poisonous thallium oxide. The reaction is as follows:

2Tl(s) + O2(g) → Tl2O(s)

• Thallium reacts steadily with moist air or dissolves in water giving rise to a poisonous material i.e. thallium hydroxide as shown in the following reaction:

2Tl(s) + 2H2O(l) → 2TlOH(aq) + H2(g)

• Thallium reacts vigorously with the following halogens - Fluorine, Chlorine and Bromine. This leads to origination of these dihalides - thallium fluoride, thallium chloride and thallium bromide. All these are extremely poisonous and their reactions are given below:

2Tl(s) + 3F2(g) → 2TlF3(s) 

2Tl(s) + 3Cl2(g) → 2TlCl3(s) 

2Tl(s) + 3Br2(l) → 2TlBr3(s)

• Since Thallium is extremely poisonous, it dissolves at a slow speed in only sulphuric acid given as H2SO4 and Hydrochloric Acid given as Hcl.

• Thallium does not get precipitated by sulfate ions and TI(l) is not precipitated by hydroxide ions. However, TI(lll) precipitates with hydroxide as shown in the  below reaction:

2 Tl3+(aq) + 6 OH−(aq) →Tl2O3(s) [brown] + 3 H2O(l)

Structure of Thallium

Having 81 electrons, Thallium has a stable structure, and its atomic data is:  

Atomic Data of Thallium

Fun Facts

• The name Thallium comes from a Greek word – Thallos, which means a green twig. This is so connected to this metal as it had a green spectral line.

• It naturally occurs as a mix of two isotopes. However, today around 25 isotopes of Thallium have been discovered

• Thallium is suspected to even be carcinogenic. 

• It can be found as a mineral in elements such as crooksite, lorandite, and hutchinsonite. It was also discovered in iron pyrite, making it another source of Thallium. Ocean floors have manganese nodules, and a small amount of Thallium has been discovered in them as well.

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