pg 183-187 Flashcards
what are the three covalent bonding theories
lewis model, valence bonding theory and molecular orbital theory
what does the born-oppenheimer approximation mean
nuclei are heavy enough to be considered as stationary allowing schrodingers equation to be solved only for the wavefunctions of the electrons
what is the valence bond approach
shared pairs of electrons form bonds between two atoms giving a bonding orbital located between the two atoms
what is the molecular orbital approach
the atomic orbitals of the atoms in a molecule combine to form a set of molecular orbitals that are spread over the whole molecule which are said to be delocalised
positives of valence bond theory
it provides a qualitative picture of bonding and can consider series of similar molecules
positives of molecular orbital theory
more quantitive so used in computational chemistry
can look at excited states so can interpret electronic spectra
what are the resonance forms of h2
H - H H+ H- H- H+
why do resonance forms not have an independent existence
because they do not exist in rapid equilibrium they have only one wavefunction
what does the two ionic forms being weighted the same mean
there is no permanent dipole
what do the symbols in the equation for valence bond theory working out the wavefunction of a molecule mean
psi is wavefunction of the whole molecule
phi is wavefunction of a specific atom and it is specified in the brackets below
the number in the brackets is which electron is there at the atom
the lamda is a constant for the weighted ionic contribution
what shape are sp hybrid orbitals
like an hourglass with one big side and one small one
which orbitals combine in an sp hybrid
2s and 2pz
what shape are two sp hybrid orbitals from different aotms bonded together
like a quality street
what do the px orbitals bonded together look like
like a oval above and below the two nuclei
what do two py orbitals bonded together from separate atoms look like
like an oval towards you and an oval away from you
