F2 Diatomic molecules Flashcards
bond length
Mean distance between the centres of two atoms in a molecule.
For homonuclear diatomic molecules the bond length is twice the atomic radius.
bond dissociation enthalphy
Measure of the bond strength
Enthalpy change to break the bond
Features of diatomic molecules (diagram)
potential energy vs distance between nuclei
increasing destabilization vs stabilization
bond dissociation energy
bond length
covalent binding
Electrons shared between atoms
The increased electron density between the nuclei holds them together
ionic binding
Electrons transferred from one atom to another
The attraction between the oppositely charged ions holds them together
polar covalent bond
electron pair shared unequally between atoms
electronegativity
Electronegativity is the power of an atom in a molecule to attract electrons to itself
the Lewis model
Two atoms share two electrons – a bond is formed
Nobel gas electron configuration – the octet rule, filled s and p orbitals (ns^2 np^6), for both atoms
By sharing electrons the octet rule can be fulfilled
bond order
Bond order = 1/2*(# of bonding electrons - # of anti bonding electrons)
single bond = 1
double bond = 2
triple bond = 3
dative bond
Kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom.
More advanced theories than the Lewis model are … and …
They give a better understanding of the covalent bond and can be used to explain problems that the Lewis model fails to do.
the Valence bond (VB) theory
the Molecular orbital (MO) theory
Valence bond (VB) theory
Resonance forms and atomic orbital overlap (including hybrid orbitals)
Overlap of two atomic orbitals results in a bonding orbital that is located between the two atoms and contains two electrons
Molecular orbital (MO) theory
Atomic orbitals are combined into molecular orbitals that are spread over the whole molecule
The molecular orbitals are delocalized
resonance
A double-headed arrow indicates resonance and all resonance forms exist simultaneously, but the different forms do not contribute equally
Orbital labels – parity labels
g = Gerade, even
u = Ungerade, odd
