Molecular Orbitals Flashcards
What is a sigma bond?
Molecular orbitals that form by end-on overlap of atomic orbitals along the axis of the covalent bond.
What is a pi bond?
Molecular orbitals that for by side-on overlap of parallel atomic orbitals that lie perpendicular to the axis of the covalent bond.
What is orbital hybridisation?
The process of mixing atomic orbitals within an atom to generate a set of new atomic orbitals.
Describe sp^3 hybridisation?
The 2s orbital and the three 2p orbitals of carbon hybridise to form four degenerate sp ^3 hybrid orbitals.
Describe sp^2 hybridisation?
The 2s orbital and two of the 2p orbitals hybridise to form three degenerate sp^2 hybrid orbitals.
Describe sp hybridisation?
The 2s orbital and one 2p orbital hybridise to form two degenerate hybrid orbital.
What type of orbital hybridisation occurs in alkanes?
sp^3
What type of orbital hybridisation occurs in alkenes?
sp^2 hybridisation
What type of orbital hybridisation occurs in benzene and other aromatic systems?
sp^2 hybridisation
What causes electrons to be promoted from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO)?
Absorption of electromagnetic energy.
Why do most organic molecules appear colourless?
Because the energy difference between HOMO and LUMO is relatively large resulting in absorption of light from the UV region.
What is a chromophore?
A group of atoms within an organic molecule that is responsible for absorption of light in the visible region.
What is a conjugated system?
A system of adjacent unhybridised p orbitals that overlap side-on to form a molecular orbital across a number of carbon atoms.
When will a compound exhibit a complementary colour?
When the wavelength of light absorbed is in the visible region.
