7th - mo bonding on 2nd period elements Flashcards
2p orbitals are
directional
one along each cartesian axis
px py pz
when looking at mo we look at
valence electrons only
ignore core electrons
aka: lower n value
what atomic orbitals have the most efficient overlap
those with the same or similar energies
2s and 2s
why dont we consider core e-
too stable
too little energy for significant overlap
what does the cartesian axis, z do
joins 2 atoms together
what is a pi bond
when the phases of the orbital are switched/reversed when it is rotated 180
pi: 180 in oven changes it
what is a sigma bond
when the phases remain the same after being rotated 180
if a mo is formed from 2 ao in the same phase the mo will be aaaaa
sigma mo
all one phase
if a mo is formed from 2 ao (s) in opposite phases the mo will be aaaaa
sigma star s orbital
antibonding orbital
node in between the 2 phases in the mo
higher in energy
when 2 ao (p) with 2 diff phases bond they form a
the phases that are the same constructively interfere
form a burger type shape with the same phase in the middle and the 2 other phases outside.
no nodes (in phase phases interefered consteuctively)
when will u see a node in mo
when 2 opposite phases are present and next to eachother.
s orbital is a
sphere shape
p orbital is a
dumbbell shape
pz points
towards the other atom
its the axis that joins atoms.
line between 2 nucs
thats why pz is sigma, 180 rotation does nothing to its phases.
horizontal chicken leg = pz
Pepez chicken = sigma
px and py point
orthoganal
vertical chicken leg
rotation it 180 by the z axis (horizontal axis, will change its phase as it will flip)
pi bond
same phases
interact
sigma or pi
bonding mo
opposite phases
node in the middle
sigma star or pi star
antibonding mo
if a mo has both can combine to form bonding and antibonding
2s (sphere) and 2pz or y
there issss
no overall bonding
just pretend they cancel out
what bond has the largest variation in energy in a mo diagram
sigma and sigma star
the p version
why do the pi star and pi not have much of an energy gap between them
bc the pz orbitals face eachother / point towards eachother
from N to the left side
sigma is higher than pi
1
2
1
2
s and p can mix, sigma goes above pi
connect the sigma to the 2s below
from O to the right
s and p are too diff in energy + cant mix, sigma goes under pi
rule for knowing if s and p mix
add e- for both atoms
/2
8 or bigger = s and p dont mix
sigma below pi
smaller than 8 = s and p mix
sigma above pi
how can molecular orbitals be formed
overlap of atomic orbitals
what does MO help us understand
helps us understand molecular properties better
