Organic Chemistry 1.1 - Molecular Orbitals - MOs, Hybridisation, Sigma and Pi Bonding Flashcards
Molecular orbitals form when…
atomic orbitals combine
Atomic and molecular orbitals can both hold a maximum of _ electrons.
2
The ___ of molecular orbitals formed is ___ to the number of atomic orbitals that…
number, equal, combined/merged
Molecular orbitals can be ___ or ___.
bonding or *antibonding
Antibonding orbitals are represented by an _.
*
The combination of two atomic orbitals results into the formation of…
a bonding and an antibonding molecular orbital.
The bonding molecular orbital ___ both ___.
encompasses both nuclei.
What is said to be the basis of atomic bonding?
the attraction between the +ve nucleus and the -ve electrons
In a carbon atom the electrons are arranged like:
1s2, 2s2, 2p6.
Considering this, how can carbon make 4 bonds?
Hybridisation occurs between the 2s and 2p orbitals
Hybrid orbitals are formed through ___, and are a type of ___ ___.
Hybridisation, atomic orbital
Describe what happens when the 2s and 2p orbitals hybridise.
the 4 atomic orbitals merge to form 4 degenerate hybrid sp3 orbitals.
When atomic orbitals from different energy levels hybridise, they become…
degenerate (atomic orbitals on the same energy level are already degenerate)
Why are these hybrid orbitals named sp3?
because of the one s and three p orbitals that combined to make them
The numbers in hybrid orbital names refers to the number of… not the number of ___.
orbitals that hybridised to form them, electrons
Molecular orbitals are ___ and can arrange themselves into shapes such as…
degenerate, tetrahedral, trigonal planar ect
What is hybridisation?
hybridisation is the process of merging atomic orbitals within an atom to create a new type of atomic orbitals called hybrid orbitals, which are degenerate
Hybrid orbitals are a type of ___ orbital.
atomic
What is the difference between molecular and hybrid orbitals?
molecular orbitals are formed when atomic orbitals of two different atoms combine.
hybrid orbitals are formed when atomic orbitals within the same atom hybridise
What is a Sigma bond?
What is a Pi bond?
the end-on overlap of two atomic orbitals of different atoms.
the side-on overlap of two atomic orbitals of different atoms.
What is the symbol for sigma and pi?
σ, π
Do all molecules need to hybridise to form bonds?
no
The formation of a sigma or pi bond is synonymous with the formation of a ___ and an ___ molecular orbital.
bonding, antibonding
A sigma bond is also known as…
a sigma bonding molecular orbital
A pi bond is also known as…
a pi bonding molecular orbital
‘The number of atomic orbitals combined is equal to the number of molecular orbitals formed’
_ atomic orbitals combine to form a sigma or pi bond, and _ molecular orbitals form (one is ___, one is ___).
2, 2 (one bonding, one antibonding)
In a molecule of methane, the four ___ hybrid orbitals overlap __-on with the ___ atomic orbitals of four hydrogen atoms.
sp3, end-on, 1s
In a molecule of fluorine, a __ atomic orbital from each atom overlaps __-on to form the ___ bonding molecular orbital.
This demonstrates that ___ does not occur in all atoms, and is not required for sigma bonds.
2s, end, sigma.
hybridisation
2p + 2p -> __
atomic + atomic -> molecular
p^2
Pi bonds can only exist between…
p orbitals
Therefore pi bonds can never form as a result of ____ of orbitals
hybridisation
The first bond between two atoms is always a ___ bond and the rest are always ___ bonds.
sigma, pi
Pi bonds produce regions of ___ density, above and ___ the axis of the ___.
electron, below, bond
Electrons in a bonding molecular orbital stabilise the molecule because…
they are between the nuclei
The fact that electrons in bonding molecular orbitals are between the nuclei, means they have…
lower energies
Antibonding orbitals place less ___ ___ between the ___.
electron density, nuclei
In a non-polar (pure) covalent bond, where is the bonding molecular orbital?
symmetrical about the midpoint of the two atoms (halfway between the two nuclei/atoms)
In polar covalent bonds, the (bonding/antibonding) molecular orbitals are…
(bonding), asymmetrical about the midpoint of the two atoms
In a polar covalent bond, the atom with the greater ____ has a greater ___ of the ___, and is therefore…
electronegativity, share, electrons, (partially) negatively charged
Ionic compounds have extreme ___ of ___ molecular orbitals between atoms.
The bonding molecular orbital is…
asymmetry, bonding.
almost entirely around the atom with stronger electronegativity
What results in the formation of ions?
the bonding MO of two atoms being almost completely around one of them, due to the v large difference in electronegativity.
