The
tellurate ionAn ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
is TeO
42− or TeO
66−.
Unlike sulfate, tellurate is a somewhat good oxidizer; it can be reduced to
telluriteThe tellurite ion is TeO32−. A tellurite is a compound that contains this ion. An example is sodium tellurite. Tellurites are one of the more stable tellurium compounds, although they can be reduced to elemental tellurium by electrolysis or a strong reducing agent.-Acidified forms:In...
or
tellurium.
Tellurate exists in two forms,
metatellurate ion, TeO
42−, and
orthotellurate ion, TeO
66−.
Compounds include
metatellurates and
orthotellurates. Metatellurates are analogous to
sulfateIn inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
s, but they are rare. Orthotellurates are much more common and this forms most of the chemistry of tellurates.
In neutral conditions,
pentahydrogen orthotellurate ion, H
5TeO
6−, is most common; in basic conditions,
tetrahydrogen orthotellurate ion, H
4TeO
62−, is found; in acid conditions, the
orthotelluric acidTelluric acid is a chemical compound with the formula Te6. It is a white solid made up of octahedral Te6 molecules which persist in aqueous solution...
, H
6TeO
6 is formed.
Properties
The
metatellurate anion, TeO
42−, has a molecular weight of 191.60 g/mole. It belongs to the T
d molecular point group, thus it has a tetrahedral shape even though two of its oxygen atoms are double bonded.
- TeO42− → TeO32− + 1/2O2 (E0= −1.042 V)
The E
0 or standard reduction potential value is significant as it gives an indication of the strength of the tellurate ion as an oxidizing agent.
The
orthotellurate anion, TeO
66−, has a molecular weight of 223.6 g/mole. It belongs to the O
h molecular point group, thus it has an octahedral shape.
NMR spectroscopy
Tellurium has two NMR active nuclei,
123Te and
125Te.
123Te has an abundance of 0.9% and a nuclear spin (I) of 1/2.
125Te has an abundance of 7% and an equivalent nuclear spin.
125Te is more commonly performed because it has a higher sensitivity. The
metatellurate anion has a
chemical shiftIn nuclear magnetic resonance spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard. Often the position and number of chemical shifts are diagnostic of the structure of a molecule...
around 610 ppm when analyzed using
125Te NMR at 25°C at a frequency of 94.735 MHz and referenced externally against aqueous 1.0 M telluric acid.
List of some known salts involving metatellurate anions
Na
2TeO
4*2H
2O
K
2TeO
4*2H
2O
Rb
2TeO
4
Cs
2TeO
4
CaTeO
4
Al
2(TeO
4)
3
(NH
4)
2TeO
4