chapter 4: molecular structure and orbitals Flashcards
what did the lewis theory predict
regions of electrons in an atom based on sharing pairs of VE
what do electron pairs do to each other
repel each other
how do we predict the shape of the molecule
assume that the electrons are far apart from each other
what does VSEPR stand for
valence, electron, paired repulsion, theory
what is the VSEPR theory
explains why molecules can form a # of bonds
- allows us to predict the bond angles
when are electrons most stable
when they are separate from each other
what are electron domains
The region in which electrons are most likely to be found (bonding and nonbonding)
how many basic arrangements of electron groups are there
5
what is the molecular geometry
MG, the positions of the atoms
when looking at geometry in a larger molecule what should you do
look at the geometry for a particular atom rather than the whole molecule
what is the rule about polarity
just bc a molecule has polar bonds does not mean that the molecule is polar in whole
what is a nonpolar molecule
symmetrical and has a net dipole at zero, equal pull in opposite directions
what is a polar molecule
unsymmetrical and has a pull in one direction which the electronegative atoms is pulling `
what are the problems with lewis theory
gives good approximations of the bond angles but can’t be used to find actual angles, doesn’t deal with resonance
when do orbitals overlap
when bonding happens between atoms
what does increased overlapping do
brings the electrons and nuclei closer together and decreases the repulsion
what is the valence bond theory
valence atomic orbitals could hybridize before bonding took place, chemical bonds result from overlaping
what is hybridization
mixing of atomic orbitals to make a new set of degenerate orbitals
what does degenerate mean
Systems (molecules, electrons, orbitals, resonance contributors, etc.) that are of equal energy.
how many degernate orbitals in sp
2
what is the shape of sp degnerate orbital
baseball bat
what shape is the s orbtial
sphere
what shape is the p orbital
dumbbell
what shape is the d orbital
clover
what is the hybridization for electron domain of 1
s
what is the electron hybridization for a domain of 2
sp
hybridization for domain 3
sp2
hybridization for domain 4
sp3
hybridization for domain 5
sp3d
hybridization for domain 6
sp3d2
what is a sigma bond
single bond,
head to head overlap
cylindrical symmetry
what is a pi bond
double bond \
side to side overlap
which is stronger pi or sigma
pi because the overlap is greater
which correlates with free rotation
sigma bonds bc it’s not as strong
what is restricted rotation
pi bonds bc it’s stronger
what does cis- mean
same side
trans isomer
opposite sides
what is the purpose of resonance structure
accurately reflect the structure of the molecule
hybridization is based off of what
the central atom
that is the molecular orbital theory
regards molecules as a collection of nuclei and electrons
MO1
greatest e- probability is between the nucleus
MO2
greatest e- probability is on either sides of the nuclei
what is lower energy bonding or anti bonding
bonding
what is the formula for bond order
of bonding electrons - # of antibonding / 2
