Increasing covalent character increases colour intensity in compounds
the verdict
SUPPORTED
the evidence backs this
refutedsupported
the weight of evidence
1 source for · 0 against
AS REPORTEDno primary record reached; this is what the reporting says
An online scientific discussion provides molecular orbital theory reasoning showing that increased covalent character reduces the HOMO-LUMO gap, thereby making electronic excitation easier and increasing colour intensity in compounds.
# Increasing Covalent character increases Colour intensity
- Tags: inorganic-chemistry, color, periodic-trends, covalent-compounds
- Score: 10
- Views: 3,573
- Answers: 1
- Asked by: Aman RU (103 rep)
- Asked on: Jan 21, 2016
- Last active: Feb 1, 2017
- License: CC BY-SA 3.0
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## Question
I observed some trends as follows:-
- $\\ce{PbCl2}$ white and $\\ce{PbI2}$ yellow
- $\\ce{SnCl2}$ white, $\\ce{SnCl4}$ red and $\\ce{SnI4}$ black
- $\\ce{AgCl}$ white, $\\ce{AgI}$, $\\ce{AgBr}$ and $\\ce{Ag2CO3}$ yellow
In all these cases as the size of anion increases ( polarisability increases) or charge on cation increases (polarising power increases) colour exhibited becomes darker.. How does increasing covalent character affect this? Or is there any other reason?
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## Accepted Answer — Score: 11
- By: Harsh gupta (126 rep)
- Answered on: Feb 1, 2017
In molecular orbital theory, as the covalent character increases the homo-lumo gap decreases, and the excitation happens more easily. Thus the colour intensity increases.