CHEM2210 Chapter Notes - Chapter 5: Spontaneous Emission, Crystal Field Theory, Spectrophotometry
Why are low-spin d8 octahedral Ni2+ complexes are not observed? Include a
diagram showing how the d-orbitals are filled.
• Octahedral d8 ion the t2g orbitals → completely filled (two electrons in
the eg orbitals)
• Increasing or decreasing the crystal field splitting will not change the
energy difference between having one electron in each of the eg
orbitals, or having both electrons in one of the eg orbitals
i.e. either dx2-y2 or dz2.
- This energy difference is instead due to the electron
repulsion
- The system will always adopt the high spin configuration, as
this minimizes the electron repulsion of the d-shell → it
lowers the unfavourable interaction between the two
unpaired electrons by locating them in different
orbitals/different regions of space.
What are the three fundamental processes which operate in all spectroscopic
experiments? Briefly describe each process
The three fundamental processes:
1. Absorption
- An absorption event involves the absorption of a quantum of
light/energy generating an excited state configuration
2. Simulated emission
- A simulated emission even involves the simulated release of a
quantum of light/energy (due to its interaction with incident light)
generating the ground state
3. Relaxation (spontaneous emission)
- A spontaneous emission event involved the release of a
quantum of energy without the application of an external
perturbation (i.e. incident light) – also can be referred to as
relaxation process(es).
Electronic Spectroscopy
• Relies on the quantized nature of energy states – given enough
energy, an electron can be excited from its initial ground state or initial
excited state (hot band) and briefly exist in a higher energy excited
state.
• Electronic transitions involve exciting an electron from one principle
quantum state to another. Without incentive, an electron will not
transition to a higher level.
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Document Summary
Include a diagram showing how the d-orbitals are filled: octahedral d8 ion the t2g orbitals completely filled (two electrons in the eg orbitals) This energy difference is instead due to the electron repulsion. The system will always adopt the high spin configuration, as this minimizes the electron repulsion of the d-shell it lowers the unfavourable interaction between the two unpaired electrons by locating them in different orbitals/different regions of space. An absorption event involves the absorption of a quantum of light/energy generating an excited state configuration: simulated emission. A simulated emission even involves the simulated release of a quantum of light/energy (due to its interaction with incident light) generating the ground state: relaxation (spontaneous emission) A spontaneous emission event involved the release of a quantum of energy without the application of an external perturbation (i. e. incident light) also can be referred to as relaxation process(es).
