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The Element Thallium

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Definition of the Thallium Element
A soft, malleable, highly toxic metallic element which can be cut with a knife. When freshly exposed to air, thallium exhibits a metallic lustre, but soon develops a blueish-grey tinge, resembling Lead in appearance. It is used in photocells, infrared detectors, low-melting glass, and formerly in rodent and ant poisons. The Atomic Number of this element is 81 and the Element Symbol is Tl.

The Properties of the Thallium Element
Symbol of Element : Tl
Atomic Number: 81
Atomic Mass: 204.3833 amu
Melting Point: 303.5 C - 576.65 K
Boiling Point: 1457.0 C - 1730.15 K
Number of Protons/Electrons: 81
Number of Neutrons: 123
Crystal Structure: Hexagonal
Density @ 293 K: 11.85 g/cm3
Color: bluish-gray

Origin / Meaning of the name Thallium
The name originates from the Greek word 'thallos' meaning a green shoot or twig from Thallium's bright green spectral emission lines.

Periodic Table Group and Classification of the of the Thallium Element
Elements can be classified based on their physical states (States of Matter) e.g. gas, solid or liquid. This element is a solid. Thallium classified in the 'Other Metals' section which can be located in groups 13, 14, and 15 of the Periodic Table. All of these elements are solid, have a relatively high density and are opaque. Nearly 75% of all the elements in the Periodic Table are classified as metals which are detailed in the List of Metals.

The Discovery of Thallium
Thallium was discovered by Sir William Crookes  in England in 1861. Claude-Auguste Lamy and Sir William Crookes isolated the metal independent of each other in 1862.

Facts about the History of the Discovery of Thallium Element
Properties within each individual group are similar, but nevertheless vary within a group. Generally chemical activity decreases as the period increases a non-metal group and increases as the period increases within a metal group. The first element in a group is always an active metal, the last is always an inactive non-metal.

History of the Periodic Table
Check out the brief History of the Periodic Table which details dates and the names of famous scientists and chemists who contributed to the development of the Periodic Table.

Occurrence of the Thallium Element
Obtained from crookesite, hutchinsonite & lorandite

Abundances of the element in different environments
% in Universe 510-8%
% in Sun 110-7%
% in Meteorites 7.810-6%
% in Earth's Crust 0.000053%
% in Oceans 110-10%
% in Humans N/A

Associated Uses of Thallium
Photocells
Rat poison
Ant killer
Thallium bromide-iodide crystals have been used as infrared optical materials
Gamma radiation detection equipment
Medical applications for the treatment of skin infections

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