Processes Flashcards
Emission Spectrum
Energy is transferred to atoms.
The electrons within the atoms are excited and promoted to higher energy levels
When the electrons falls down to lower energy levels, energy is released as a photon of light.
Absorption spectrum
Electromagnetic radiation is directed at an atomised sample.
Radiation is absorbed and electrons are promoted to higher energy levels.
An absorption spectrum is produced by measuring how the intensity of ABSORBED light varies with wavelength.
Transition metal colour
An isolated TM ion contains 5 degenerate d atomic orbitals.
When a ligand approaches the TM ion, the TM ion’s electrons are repelled by the electrons from the ligand.
This results in splitting of the d atomic orbitals.
When light of a specific wavelength is absorbed, electrons can be promoted to higher energy d orbitals.
If absorbed light is from the Visible spectrum (400-700nm), then the colour produced is complementary to the absorbed colour.
To explain how a solution becomes acidic.
Because this is Acidic, there must be an XS of H+ ions.
The OH- ions react with the large concentration of positive ions, leaving an XS of H+ ions, resulting in the acidic solution.
To explain how a solution becomes basic.
Because this is Basic, there must be an XS of OH- ions.
The H+ ions react with the large concentration of negative ions, leaving an XS of OH- ions, resulting in the basic solution.
Steps in Homolytic fission
Has 3 main steps :
Initiation
Propagation
Termination
Heterolytic fission
When a bond breaks heterolytically, both electrons move onto one atom.
The more electronegative atom of the bond retains both electrons and ends up as a negatively charged ion.
Steps in Mass Spectroscopy
A minute sample of the UNKNOWN organic compound is :
Heated
Ionised by fast moving electrons to form + ions
The + ions are passed through an electric field into a strong magnetic field
This deflects the ions into a series of separate ion paths according to their mass/charge ratio
The peak farthest right is the Molecular Ion Peak, this mass equates to the GFM.
Steps in IR Spectroscopy
IR radiation is passed through a sample of the organic compound.
This is then passed into a detector
The detector measures the intensity of transmitted radiation at different wavelengths.
TMS
Used in NMR spectroscopy.
The molecule whose structure is being determined is dissolved in a reference substance which is TMS - Tetra Methyl Silane
It is assigned a value of zero
The bonding continuum
Non Polar covalent bonding
The bonding molecular orbital is completely symmetrical about the MIDPOINT between 2 atoms of the bond.
Polar covalent bonding
The bonding molecular orbitals is asymmetrical about the midpoint between the 2 atoms.
Ionic bonding
The bonding molecular orbital is almost entirely located around just 1 atom, resulting in the formation of ions.
Colour in organic molecules
The absorption of electromagnetic energy can cause electrons to be promoted from the HOMO to the LUMO.
If the energy gap between the HOMO and LUMO is too large (i.e. wavelength is small) then the molecule will appear colourless, as it is absorbing light in the UV region.
Some carbon compounds contain a group of atoms that absorb light in the visible region called a chromophore.
The electrons in the chromophore can absorb light and cause the electrons to be promoted from the HOMO to LUMO.
These organic molecules which are coloured have CONJUGATION.
Degree of conjugation
As the degree of conjugation increases, the gap between the HOMO and LUMO decreases.
So light of a longer wavelength will be absorbed. (i.e. from the visible region)
We observe the complementary colour.
