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Tellurites can be extracted from the mixture with water and are normally present as hydrotellurites HTeO 3 - in solution.Selenates are also formed during this process, but they can be separated by adding sulfuric acid. The hydrotellurites are converted into the insoluble tellurium dioxide while the selenites stay in solution, [link] .

The reduction to the metal is done either by electrolysis or by reacting the tellurium dioxide with sulfur dioxide in sulfuric acid, [link] .

Physical properties

The physical properties of the Group 16 elements encompasses a gas (O 2 ), a non-metallic solid (S 2 ), and metals (Se, Te, Po), [link] .

Selected physical properties of the Group 16 elements.
Element Mp (°C) Bp (°C) Density (g/cm 3 )
O -218.79 -182.95 1.429 g/L
S 115.21 444.6 1.819
Se 221 685 4.81 (gray), 4.39 (alpha), 4.28 (vitreous)
Te 449.51 988 6.24 (solid), 5.70 (liquid)
Po 254 962 9.196 (alpha), 9.398 (beta)

Vapor phase

The lighter Group 16 elements form X 2 dimers in the vapor phase. Sulfur also forms higher allotropes in the vapor phase (e.g., S 8 and S 6 ), while selenium and tellurium forms atomic vapor in addition to the dimmers. Unlike dihydrogen, however, the bonding is associated with the molecular orbital combination of the two π-orbitals ( [link] ). All of the dimeric X 2 molecules are paramagnetic.

Molecular orbital diagram for the formation of O 2 .

Solid state

While sulfur forms over 30 allotropes, the common form of sulfur is cyclooctasulfur (S8) has three main allotropes: Sα, Sβ, and Sγ. The orthorhombic form (Sα) is more stable up to 95 °C, while the β-form is the thermodynamic form. The lone pairs of electrons make the S-S-S bend (108°), resulting in S 8 having the shape of a crown ( [link] ). When sulfur melts the S 8 molecules break up. When suddenly cooled, long chain molecules are formed in the plastic sulfur that, behave as rubber. Plastic sulfur transform into rhombic sulfur over time.

The structure of S 8 .

Elemental selenium produced in chemical reactions appears as the amorphous red form. When rapidly melted, it forms the black, vitreous form, which is usually sold industrially as beads. The most thermodynamically stable and dense form of selenium is the electrically conductive gray (trigonal) form, which is composed of long helical chains of selenium atoms ( [link] ). The conductivity of gray selenium is light sensitive and is hence used in photocopiers. Selenium also exists in three different deep-red crystalline monoclinic forms, which are composed of Se8 molecules, similar to many allotropes of sulfur. Unlike sulfur, however, selenium does not undergo the changes in viscosity when heated.

Tellurium is a crystalline metal with a triginal structure ( a = 4.4572 Å, c = 5.929 Å). Polonium has a simple cubic structure in it’s a form ( a = 3.359 Å)

Compounds of the group 16 elements.

The chemistry of the Group 16 elements is dominated by the stability of the -2 oxidation state and the noble gas configuration of the X 2- anion.

Oxidation state

The electronegativity of oxygen (3.5) results in it having predominantly -2 oxidation state, however, sulfur, selenium and tellurium all for compounds with higher oxidation states, especially with oxygen ( [link] ).

Examples of oxidation states in compounds of the Group 16 elements.
Element -2 -1 +4 +6
O Na 2 O, H 2 O H 2 O 2 - -
S H 2 S H 2 S 2 SO 2 H 2 SO 4 , SO 3
Se H 2 Se H 2 Se 2 SeO 2 SeF 4
Te H 2 Te t Bu 2 Te 2 TeO 2 Te(OH) 6


Catenation is the ability of a chemical element to form a long chain-like structure via a series of covalent bonds. Although oxygen shows this property only in the existence of ozone, sulfur is second only to carbon in exhibiting this mode of combination; the chalcogens beyond sulfur show it to diminishing degrees, polonium having no tendency to catenate.

When aqueous metal sulfide salts are heated with elemental sulfur a range of polysulfide ions are formed, [link] . When alkali polysulfides dissolve in polar solvents (e.g., DMF or DMSO) a deep blue solution is formed. The absorption (λ max = 610 nm) is associated with the radical anion, S 3 - . While, polyselenides and polytellurides are less common, the Se 3 2- and Te 3 2- ions are known.

The term polysulfide often refers to a class of polymers with alternating chains of several sulfur atoms and hydrocarbon substituents. The general formula is R 2 Sn, where n ranges from 2 – 10. For the selenium and tellurium analogs the extent of catenation is far more limited.


  • D. Barisic, S. Lulic, and P. Miletic, Water Research , 1992, 26 , 607.
  • M. Davies, History of Science, 1989, 22 , 63.
  • T. F. Kelley, Science , 1965, 149 , 537.
  • M. B. Power, J. W. Ziller, A. N. Tyler, and A. R. Barron, Organometallics ., 1992, 11 , 1055.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
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Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
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I think
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Brian Reply
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scanning tunneling microscope
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Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
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The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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Damian Reply
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Stoney Reply
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Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
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biomolecules are e building blocks of every organics and inorganic materials.
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, Chemistry of the main group elements. OpenStax CNX. Aug 20, 2010 Download for free at http://cnx.org/content/col11124/1.25
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