Molecular Orbital Theory Flashcards
2 1s subshells combine to form a
Sigma molecular orbital
New molecular orbital that forms from 2 hydrogens combining is the
Sigma Star * molecular orbital
Bonding molecular orbitals energy is ?
Lower
Anti-bonding molecular orbitals energy is?
Higher
Lower energy orbitals?
Lower the entire energy of our system
Bond Order is calculated how?
(# of bonding electrons - # of anti-bonding electrons) /2
How many bonds does a hydrogen molecule have?
1 single bond
The # of Atomic Orbitals must be ?
Equal to the # of molecular orbitals energy
Hydrogen atom with atomic orbital and sigma star molecular orbital
Atomic orbitals are
Non-bonding energy
If you have 2 unbonded electrons in atomic orbitals, how many electrons combine to form bonded molecular orbitals ?
Each unbonded electron in an atomic orbital combines with an electron from the other molecule its combining with in the molecular orbital so the number of electrons doubles in the molecular orbital in the center to show how the 2 side atomic orbitals combine in the center. Each atom on a side, combination of the 2 in the center like the combination of these 2 hydrogen atoms
Bond order is calculated how?
The number of bonding electrons minus the number of anti bonding electrons then divide that by 2.
For hydrogen we have 2 bonding electrons minus 0 anti bonding electrons so that’s 2 divided by 2 = 1 bond
When the sigma bond is formed, the energy does what?
Goes down
When the sigma star* bond is formed, the energy does what?
The energy increases to populate the higher sigma star orbital
Can 2 helium atoms bond?
No bc they have 2 bonding electrons minus 2 anti bonding electrons = 0 divided by 2 = 0 no bonds
HELIUM EXISTS AS ISOLATED ATOMS
Pi and pi*star bonds form from what MO’s- molecular orbitals?
P orbitals
Sigma and Sigma*Star bonds form from what MO’s-molecular orbitals ?
S orbitals
With bond pictures, we are only looking at the
outer shell for bonding which can be the s orbital or it can be the p orbital, etc. depending on what atoms we are looking at
Anti bonding MOs do what do energy?
Increase energy
Bonding MOs do what to energy?
Bonding Molecular Orbitals decreases energy, bc it takes energy to bond so it put out energy and its overall energy decreases
The anti-bonding orbitals show all the electrons each side atomic has
The center bonding orbitals show how 1 electron of each side comes to join in the center with 1 from the other side and 1 from each box comes to the center first before the 2nd electron from each box comes to the center bonding molecular orbital.
If there are 6 atomic orbitals filled, how many molecular orbitals can be filled?
We must have 6 also, these numbers must match
2 electrons can go in each orbital but not all elements will fill all orbitals with 2 electrons
Anti bonding electrons still bond into the higher orbit and labeled
Pie star *
The first electron that comes out of each orbital make up your?
Bonding electrons
The left over electrons that come out of each orbital second are your ?
Anti bonding electrons
Your bond order is calculated how?
(Bonding electrons minus anti-bonding e-) divided by 2
Diatomic molecules have what type of bond?
Double bond - pie bond
In Valence Bond Theory, all electrons are paired which would make it
Diamagnetic
(Repelled by a magnet)
Is O2 diatomic molecule paramagnetic or diamagnetic?
Paramagnetic (attracted to a magnet)
It should be diamagnetic bc all electrons are paired but this is an exception
The orbital diagram can be split into 3 parts which are:
Left, right, middle
Left shows atom on left for bonding
Right shows atom on right for bonding
Middle shows molecule bonded
How does energy increase in an orbital diagram?
Energy increases as you travel up the diagram from bottom to top
The bottom 1s sigma orbital is called
A bonding molecular orbital, which has LOWER Energy (at bottom) but
GREATER Stability (like the base of a structure is the most stable)
The top 1s sigma star* orbital is what type of orbital ?
What is its energy and stability like?
Anti-bonding molecular orbital
HIGHER Energy (higher up)
LESS Stable than the atomic orbitals that
formed it
(Compared to the 1s atoms that it was formed from)
What does the star indicated on the sigma orbitals?
The star indicates that it is anti-bonding
(Higher energy, less stable=anti-bonding)
Hydrogen is what type of molecule?
Diatomic molecule, comes in pairs
H—H
1 double bond 2 atoms, 1 electron each
