Formation of coloured ions Flashcards
What happens when ligands bond to the ions?
Some orbitals are given more energy than others
What orbitals do the electrons occupy?
Lower orbitals
What do the electrons need to jump up to the higher orbitals?
They need energy equal to the energy gap
Where do electrons get the energy from to jump up energy state?
From visible light
What equation is used to calculate the light energy absorbed by the electrons?
∆E = hv = hc/λ
What is the unit for ∆E?
J
What is h?
Planck’s constant
What is v?
Frequency of light absorbed
What is c?
the speed of light
What is the value for the speed of light?
3.00 x 10⁸ m s⁻¹
what is λ?
Wavelength of light
What is the unit for λ?
m
What are the units for v?
Hertz
what is the value for Planck’s constant?
6.63 x 10-³⁴ Js
Why do you see colours of compounds?
some frequencies are absorbed as electrons jump up to the higher orbitals and the light frequencies not absorbed are reflected and thats the colour you see
Why does you see a colourless solution sometimes?
If there are no 3d electrons or the 3d sub-level is formed
no electrons will jump, no light absorbed
all light reflected
What three things can you use to identify transition metal ions?
Changes in oxidation state
Changes in co-ordination number
Changes in ligand
How is spectroscopy used to determine the concentration of a solution?
- white light is shone through a filter which is chosen to only let the colour of light through that is absorbed by the sample
- Then light passes through the sample to a colorimeter which shows how much light was absorbed by the sample
- plot a calibration graph
The more concentrated a coloured solution…
…the more light it will absorb
How do you calculate an unknown concentration of a solution?
- Produce a calibration curve of the known concentration values
- Concentration on the x axis
- Relative absorbance on the y axis
- Then use the relative absorbance to look at the concentration of the unknown sample
