Card Set Information
Types of bonding, what type of element they're between, and how e
ionic (metals to nonmetals) - e
covalent (nonmetals to nonmetals) - e
metallic (metal to metal) - e
Bond type by electronegativitiy
0.0 = pure covalent
0.1 - 0.4 = nonpolar covalent
0.5 - 1.9 = polar covalent
2.0 - 4.0 = ionic
Octet rule exceptions
H, He have only 2 e
Group IIIA elements may have 6 e
Elements in period 3+ may have 8, 10, 12, or 14 e
The only 3 free radical compounds (exceptions to lone pair rule)
, and ClO
How do you check a Lewis Dot Diagram?
Correct # of e
Σ Formal Charges = charge of molecule?
Trends in bond length
shared by atoms = shorter covalent bond
Bond length decreases from left to right across period
Bond length increases down the column
Trends in bond energy (energy needed to break a bond)
shared by atoms = stronger covalent bond
Shorter covalent bond = stronger covalent bond
Using bond energies to estimate ΔH
Evaluating resonance structures
Better structures have fewer formal charges
Better structures have smaller formal charges
Better structures have negative formal charges on more electronegative atoms
Possible shapes of molecules with VSEPR formula and bond angle
- linear - 180˚
AX3 - trigonal planar - 120˚
E - v shaped/bent
- tetrahedral - 109.5˚
E - trigonal pyramidal
- v shaped/bent
- trigonal bipyramidal - 120˚ (equatorial) and 90˚ (axial to equatorial)
E - irregular tetrahedral / seesaw
- T shaped
- octahedral - 90˚
E - square pyramidal
- square planar
How do lone pairs affect bond angle?
Lone pair "take up more space" and decrease the bond angle between atoms
How to draw 3D object on 2D plane
solid line - on the same plane as the paper
solid bar - in front of plane
dashed bar - behind plane
Which shapes result in non-polar molecules (through vector cancellation) and which shapes result in polar molecules (uncancelled vectors)?
: linear, trigonal planar, tetrahedral, tigonal bipyramidal, octahedral, square planar
: bent, trigonal pyramidal, seesaw, t-shaped, square pyramidal
How does Valence bond theory explain bonding? List the hybrids, and their corelation to Lewis dot.
VBR states that a bond is the overlap of atomic (or hybrid) orbitals.
Hybrids are created based on the lewis dot structure, based on how many e
densitites the atom has.
2 (sp), 3 (sp
), 4 (sp
), 5 (sp
d), 6 (sp
How do you know how MANY hybrid orbitals to use?
The number of atomic orbitals combined = the number of hybrids formed
eg combining a 2s with a 2p gives 2 sp orbitals
Describe the different types of bonds using greek letters, and how each overlaps in depth.
1 single bond = 1
1 double bond = 1
δ bond and 1
1 triple bond = 1
δ bond and 2
δ bonds overlap once, along the axis of the bond using hybrid orbitals
π bonds overlap twice, perpendicular to axis using unhybridized p orbitals
Explain the steps in proving a hybridization
Draw the lewis dot structure
Get the electron configuration for the element
Establish hybridization based on lewis dot
Draw energy levels using electron configuration
Create hybrids and fill in the electrons, make sure it matches (remember p orbitals are unhybridized in
How does Molecular orbit theory explain bonding?
Electrons belong to whole molecule, orbitals belong to whole molecule (delocalization)
Differences between VBT, MO, and Lewis
VBT predicts many properties better than Lewis (bonding schemes, bond length, bond strengths, bond rigidity)
VB presumes electrons are localized, and does not account for delocalization
VB cannot predict perfectly (magnetic behavior)
MO can predict bond order, energies, magnetic properties
Both are used, but have strengths and weaknesses
What forms a bonding molecular orbital? What are the symbols?
When the two wave functions combine constructively the resulting molecular orbital has less energy than the original atomic orbital
π are bonding orbitals (most electon density between nuclei)
What forms a antibonding molecular orbital? What are the symbols?
When the two wave functions combine deconstructively the resulting molecular orbital has more energy than the original atomic orbitals
π* are antibonding orbitals (most electon density outside nuclei)
nodes (spaces without electrons) between nuclei
What is bond order?
(Bonding electrons - antibonding electrons) / 2
Only use valence electrons
higher bond order = stronger/shorter bonds
MO paramagnetic vs diamagnetic
paramagnetic (attracted to magnets) if MO diagram has unpared electrons
diamagnetic (not attracted to magnets) if MO diagram has all electrons paired
LUMO, HOMO, and what they are used for.
Lowest Unpaired Molecular Orbit
Highest Occupied Molecular Orbit
Difference is used to determine wavelength absorpotion by molecule
Name of structure that ions form?
What is lattice energy (
)? Formulaic definition? What formula/factors affect lattice energy?
Energy released when 1 mol solid crystal forms from ions in gas state
-> 1 mol molecule
Depends on size/charge of ions [direct] and distance between ions [inverse]
E = C x q