What is the geometry of the #"manganate ion"#, #MnO_4^(2-)#?

2 Answers
Aug 9, 2017

Answer:

Tetrahedral.......

Explanation:

We have #Mn(VI)#, i.e. #(O=)_2MnO_2^(2-)#, and thus manganate is an analogue of sulfate ion, for which we can use VSEPR directly.....

Aug 9, 2017

Answer:

The geometrical shape is tetrahedral.

Explanation:

1. Decide which is the central atom in the structure.

That is normally the least electronegative atom (#"Mn"#).

2. Draw a skeleton structure in which the other atoms are single-bonded to the central atom:

#color(white)(mml)"O"#
#color(white)(mmll)|#
#"O—Mn—O"#
#color(white)(mmll)|#
#color(white)(mml)"O"#

3. Put electron pairs around every atom until each gets an octet.

#color(white)(mm)":Ö:"#
#color(white)(mmll)|#
#":Ö—Mn—Ö:"#
#color(white)(m)" ̈ color(white)(ml)|color(white)(mml) ̈#
#color(white)(mm)":O:"#
#color(white)(mmm) ̈ #

4. Count the valence electrons in your trial structure (32).

5. Now count the valence electrons you actually have available.

#"1 Mn + 4 O + 2e"^"-" = 1×2 + 4×6 + 2 = 28"#.

The trial structure is missing four electrons.

6. Draw a new structure, this time inserting one double bond for each missing pair of electrons and giving each #"O"# atom an octet:

#color(white)(mm)":Ö:"#
#color(white)(mmll)|#
#":Ö=Mn=Ö:"#
#color(white)(mmll)|#
#color(white)(mm)":O:"#
#color(white)(mmm) ̈ #

Note: The #"Mn"# atom can have an "expanded" octet.

7. Use VSEPR theory to determine the molecular geometry.

There are four bonding electron domains and no lone pairs about the #"Mn"# atom.

This is an #"AX"_4# molecule.

www.chemthes.com

The molecular geometry is tetrahedral.

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