Dichromate (VI) Cr2O7-2

[Romix]

Hello all.

Can some one expain me please how this double bonds are formed?

Edited September 6, 2014 by Romix

[fiveworlds]

http://www.chemguide.co.uk/atoms/bonding/doublebonds.html

[Romix]

oooo that's my mistake I counted chromium as (V) and it's (VI)

Edited September 6, 2014 by Romix

[fiveworlds]

Polar http://en.wikipedia.org/wiki/Chemical_polarity

Ozone is similar

Caused By the incomplete sharing of an electron pair.

Edited September 6, 2014 by fiveworlds

[Romix]

 

like this ?

Ok all Oxygens are happy, they have full outer valence shells of 8 electrons.

But chromium have 12 now! Something not right here.

Edited September 6, 2014 by Romix

[fiveworlds]

Cr's electron configuration, following the model would be: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²3d⁴, but instead it is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹3d⁵, because there is extra stability gained from the half-filled d orbital.

 

Now you bond Chromium with oxygen. Chromium will be most stable 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²3d¹⁰

^{Therefore chromium wants 6 electrons from oxygen. The middle oxygen takes 1 all the time and the remaining three oxygens incompletely share the remaining 5 electrons. All the oxygens want 2 electrons.}

Edited September 6, 2014 by fiveworlds