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TitleThallium
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THALLIUM

Thallium is a member of the aluminum family, Group 13 (IIIA) on the periodic table. The

periodic table is a chart that shows how chemical elements are related to one another.

Thallium is also a member of the heavy metals, along with gold,

platinum, and lead.Thallium was first discovered by means of a

spectroscope. A spectroscope is a device for analyzing the light

produced when an element is heated. The spectrural

(plural: spectra) of an element consists of a series of colored lines

that are different for every element. The brightest lines in the spectrum of thallium are

green, which accounts for its name. In Greek, the word thallos means "green twig." The

green lines in thallium's spectrum look like green twigs.Its atomic number is 81 and

atomic mass is 204.37.Thallium is a rather uncommon element. Still, some of its

compounds have important applications. For example, thallium sulfate (Tl 2 SO 4 ) has

long been used as a rodenticide (rat and mouse poison). One form of thallium is

sometimes used to study the flow of blood in the body. It shows how well the heart is

working.





Discovery and naming:

The spectroscope was invented in 1814 by German physicist Joseph von Fraunhofer

(1787-1826). Forty years later, German chemists Robert Bunsen (1811-99) and Gustav

Robert Kirchhoff (1824-87) improved on the instrument and showed how it could be

used to study chemical elements. (See sidebar on Bunsen in the cesiumentry in Volume

1.)

Scientists were fascinated by the instrument. They could detect the presence of

elements without actually seeing them. A mineral is made of many elements, each of

which gives off its own series of colored (spectral) lines. The spectroscope is able to

detect all the elements present in the mineral.

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camera records the radiation given off by the isotope. This record shows whether the

patient's heart is working properly or not.

Electron Configuration:


1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p1



Electron per EnergyLevel:



2,8,18,32,18,3

Extraction:

Thallium is obtained as a by-product of the recovery of lead and zinc. Gases from the

recovery process are captured. They are then treated to obtain the pure metal.

Uses and compunds:

For many years, thallium sulfate (Tl 2 SO 4 ) was used as a rodenticide. It worked well

with rats and mice because it passes through their skin easily. Once inside their bodies,

it causes.

death. Thallium sulfate is also colorless and odorless, so rats and mice were not aware

the compound was present.

Unfortunately, thallium sulfate has the same effects on humans. Accidental poisoning,

especially of young children, led to the banning of thallium sulfate as a rodenticide in the

United States in 1975. Today, safer compounds (for humans, not rats) are available for

rodenticides.

Thallium is too expensive to have many practical applications. There are a few

exceptions, however, that make use of special properties of the elements and its

compounds. For example, thallium sulfide (Tl 2 S) is sometimes used in photocells.

Photocells are devices that convert light into electrical energy. In some kinds of light,

thallium sulfide does not conduct electricity very well. But in other kinds of light, it

conducts very well. Special photocells can be built to take advantage of this property.

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