The tellurate ion

Ion

An 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 TeO₄²⁻ or TeO₆⁶⁻.

Unlike sulfate, tellurate is a somewhat good oxidizer; it can be reduced to tellurite

Tellurite (ion)

The 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, TeO₄²⁻, and orthotellurate ion, TeO₆⁶⁻.

Compounds include metatellurates and orthotellurates. Metatellurates are analogous to sulfate

Sulfate

In 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, H₅TeO₆⁻, is most common; in basic conditions, tetrahydrogen orthotellurate ion, H₄TeO₆²⁻, is found; in acid conditions, the orthotelluric acid

Telluric acid

Telluric 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...

, H₆TeO₆ is formed.

Properties

The metatellurate anion, TeO₄²⁻, 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 E⁰ 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, TeO₆⁶⁻, 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 shift

Chemical shift

In 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

Na₂TeO₄*2H₂O

K₂TeO₄*2H₂O

Rb₂TeO₄

Cs₂TeO₄

CaTeO₄

Al₂(TeO₄)₃

(NH₄)₂TeO₄