molecular orbitals Flashcards
(33 cards)
what can molecular orbital provide an explanation for
VSEPR cannot explain the bonding in all compounds. Molecular orbital theory can provide an explanation for more complex molecules.
when do molecular orbitals form
Molecular orbitals form when atomic orbitals combine.
what is the number of molecular orbitals formed equal to
The number of molecular orbitals formed is equal to the number of atomic orbitals that combine.
what is result of the combination of two
atomic orbitals
The combination of two
atomic orbitals results in the formation of a bonding molecular orbital and an antibonding orbital.
what does the bonding molecular orbital encompass
The bonding molecular orbital encompasses both nuclei.
What is the basis of bonding between atoms
The attraction of the
positively charged nuclei and the negatively charged electrons in the bonding molecular orbital is the basis of bonding between atoms.
In a non-polar covalent bond what is the bonding molecular orbital
In a non-polar covalent bond, the bonding molecular orbital is symmetrical about the
midpoint between two atoms.
what do Polar covalent bonds result in
Polar covalent bonds result from bonding molecular orbitals that are asymmetric about the midpoint between two atoms.
The atom with the greater
value for electronegativity has what?
The atom with the greater
value for electronegativity has the greater share of the bonding electrons.
Ionic compounds
are an extreme case of what?
Ionic compounds
are an extreme case of asymmetry, with the bonding molecular orbitals being almost entirely located around just one atom, resulting in the formation of ions.
what are sigma molecular orbitals/ sigma bonds
Molecular orbitals that form by end-on overlap of atomic orbitals along the axis of the
covalent bond are called sigma (σ ) molecular orbitals or sigma bonds.
what are pi bonds
Molecular orbitals that form by side-on overlap of parallel atomic orbitals that lie perpendicular to the axis of the covalent bond are called pi (π ) molecular orbitals or
pi bonds.
what can the electronic configuration of an isolated carbon atom not explain
The electronic configuration of an isolated carbon atom cannot explain the number of bonds formed by carbon atoms in molecules
how is the bonding and shape of molecules of carbon explained
The bonding and shape of molecules of carbon can be explained by hybridisation.
in alkanes the 2s orbital and the three 2p orbitals of carbon hybridise to form what?
In alkanes, the 2s orbital and the three 2p orbitals of carbon hybridise to form four degenerate sp3 hybrid orbitals. These adopt a tetrahedral arrangement. The sp3 hybrid orbitals overlap end-on with other atomic orbitals to form σ bonds.
what can the bondiing in alkenes be described in terms of
The bonding in alkenes can be described in terms of sp2 hybridisation. The 2s orbital and two of the 2p orbitals hybridise to form three degenerate sp2 hybrid orbitals. These adopt a
trigonal planar arrangement.
The hybrid sp2 orbitals overlap end-on to form σ bonds. what do the remaining 2p orbitals
The hybrid sp2 orbitals overlap end-on to form σ bonds. The remaining 2p orbital on each carbon atom of the double bond is unhybridised and lies
perpendicular to the axis of the σ bond. The unhybridised p orbitals overlap side-on to form π bonds.
what can the bonding in benzene and other aromatic systems can be described in terms of
The bonding in benzene and other aromatic systems can be described in terms of sp2
hybridisation.
how are the 6 carbon atoms in benzene arranged
The six carbon atoms in benzene are arranged in a cyclic structure with σ bonds between the carbon atoms. The unhybridised p orbitals on each carbon atom overlap side-on to form a π molecular system, perpendicular to the plane of the σ bonds. This π molecular system extends across all six carbon atoms. The electrons in this
system are delocalised.
how can the bonding in alkyenes be described in terms of
The bonding in alkynes can be described in terms of sp hybridisation. The 2s orbital and one 2p orbital of carbon hybridise to form two degenerate hybrid orbitals
These adopt a linear arrangement. The hybrid sp orbitals overlap end-on to form σ bonds. The remaining two 2p orbitals on each carbon atom lie perpendicular to each other and to the axis of the σ bond. The unhybridised p orbitals overlap side-on to form two π bonds.
what can molecular orbital theory be used to explain
Molecular orbital theory can be used to explain why organic molecules are colourless or coloured.
what leaves antibonding orbitals unfilled
Electrons fill bonding molecular orbitals, leaving higher energy antibonding orbitals unfilled.
what is homo and what is lumo
The highest bonding molecular orbital containing electrons is called the highest occupied molecular orbital (HOMO). The lowest antibonding molecular orbital is called the lowest unoccupied molecular orbital (LUMO).
