Question

Why is the Carbonate ion colourless while the permanganate ion is? It was told the permanganate ion gets the colour by the electron movement within the Oxygen atoms due to the hybrid. Cannot that happen in Carbonate ions as well? I was thinking using MOT there are no unpaired electrons in the Carbonate ion and that might be the reason. Then I tried to draw the MOD of permanganate ion and failed miserably. Any help please?

And I have my inorganic exam tomorrow so quick help appreciated very much

Answer 1

,

Answer 2

due to Mn which is transition elemt and transition elements show colours due to d_d transition

Answer 3

but Mn is in +7 state so there are no d electrons for transition to happen

Answer 4

Ar] 4s2 3d5 this is electronic confriguation of Mn

Answer 5

ikr.in permanganate ion it has reached +7 oxidation state. Just like Ti +4 ions are colourless

Answer 6

Permanganate (+7 oxidation state) compounds are purple, and can give glass a violet color.. is due to a spin-forbidden 3d transition, which is rare.

Answer 7

Titanium(III) chloride TiCl3 is a violet solid.

Answer 8

Titanium(II) chloride TiCl2 is a black solid.

Answer 9

the colourless oxotitanium(IV) ion is reduced to the purple hexaaquatitanium(III) ion

Answer 10

Note that Ti4+ has a [Ar]3d0 structure, hence, with no 3d electrons it is colourless

Answer 11

that is what I meant as well, the same happens in Mn7+

Answer 12

no MOT cant help u, CO3 has carbon which isnt transition element.Mn is a transition element and it is its chemical property to show different colours at different oxidation states in a complex

Answer 13

what about LMCT and MLCT.
there are none of them in carbonate.

Answer 14

i think that may well be the answer, read about LMCT in a forum but didn't really get it. Can you please explain a bit :) I haven't learnt that yet

Answer 15

yes. simply talking. when we have a complex (not only ligand nor only metal) this phenomena happens.

LMCT complexes arise from transfer of electrons from MO with ligand like character to those with metal like character. it means that ligand gives charge to metal. MLCT is vice versa.

useful link:
http://en.wikipedia.org/wiki/Charge-transfer_complex

Answer 16

Color of charge-transfer complexes
Many metal complexes are colored due to d-d electronic transitions. Visible light of the correct wavelength is absorbed, promoting a lower d-electron to a higher excited state. This absorption of light causes color. These colors are usually quite faint, though. This is because of two selection rules:
The spin rule: Δ S = 0
On promotion, the electron should not experience a change in spin. Electronic transitions which experience a change in spin are said to be spin forbidden.
Laporte's rule: Δ l = ± 1
d-d transitions for complexes which have a center of symmetry are forbidden
Charge-transfer complexes do not experience d-d transitions. Thus, these rules do not apply and the absorptions are generally very intense.
For example, the classic example of a charge-transfer complex is that between iodine and starch to form an intense purple color. This has widespread use as a rough screen for counterfeit currency. Unlike most paper, the paper used in US currency is not sized with starch. Thus, formation of this purple color on application of an iodine solution indicates a counterfeit.

Answer 17

i find out above explanation in wikipedia.did u get this?anymore confusion?please ask......thanks