CHEM 110 - FINAL Flashcards
Which kind of bond has the shortest bond length?
Triple Bond
Which bond has the longest bond length?
Single Bond
Which bond is the strongest and most difficult to break?
Triple bond
Electronegativity trend ____ across a period and ______ along the groups
increases (to the right), increases (up)
What electronegative values classify a covalent bond?
0
What electronegative values classify an ionic bond?
> or equal to 2
What electronegative values classify a polar covalent bond?
Values between 0 and 2
Increasing bond polarity is present when _____.
there is a dipole moment or when there are large differences in electronegativity (ie. Lithium bonding with Cl and they are far away from each other on the periodic table)
Formal charge formula?
(total # of valence electrons) - (total # of nonbonding electrons) - 1/2 (total # of bonding electrons)
Why is BF3 an exception to the octet rule?
B does not complete the octet (only forms 3 bonds)
Why is SF6 an exception to the octet rule?
It has an expanded octet - sulfur has d-orbitals that allow the element to bond to more than 3 atoms
Why is NO an exception to the octet rule?
Results in odd electron molecules (where N has 3 lone electrons)
How do you calculate bond enthalpy in a reaction?
Subtract products of bond enthalpies (would have to be given specific values) from the reactants
(Also multiply by the bond enthalpies coefficients in the reaction as well!)
Bond angle of tetrahedral geometry?
109.5 degrees
VSEPR model vs. molecular geometry?
VSEPR model: expresses how electron groups are arranged - named based on electrons repelling each other
Molecular geometry: 3D arrangement of atoms in a molecule - named based on the atom arrangement
When do VSEPR and molecular geometry names line up?
Generally when there are no lone pairs (ie. CH4 will have an electron geometry AND molecular geometry of tetrahedral)
Bond angle for linear compounds?
180 degrees
What is the greatest repulsive interaction within a compound?
lone-pair repulsion vs. lone pair repulsion
A lone pair will _____ the bond angle between bonding pairs (increase/decrease)
decrease
Lone pairs prefer to occupy ____ positions because they are weaker than ____ positiions
equatorial; axial
A species will be nonpolar overall if _____
1) individual bond dipoles cancel
OR
2) has identical bonds and a symmetrical geometry
A species will be polar overall if ___
1) individual bond dipoles do not cancel
OR
2) has an unsymmetrical geometry
Is CCl4 polar or nonpolar?
Nonpolar; it has C-Cl dipoles but they cancel out
AB2 - Molecular Geometry & VSEPR?
Linear
AB3 - Molecular Geometry & VSEPR?
Trigonal Planar
AB4 MG & VSEPR?
Tetrahedral
AB5 MG & VSEPR?
Trigonal bipyramidal
AB6 MG & VSEPR?
Octahedral
AB2E VSEPR?
Trigonal planar
AB2E MG?
Bent
AB3E VSEPR?
Tetrahedral
AB3E MG?
Trigonal pyramidal
AB2E2 MG?
Bent
AB2E2 VSEPR?
Tetrahedral
AB4E VSEPR?
Trigonal bipyramidal
AB4E MG?
Distorted tetrahedral
AB3E2 VSEPR?
Trigonal bipyramidal
AB3E2 MG?
T-shaped
AB2E3 VSEPR?
Trigonal bipyramidal
AB2E3 MG?
Linear
AB5E VSEPR?
Octahedral
AB5E MG?
Square pyramidal
AB4E2 VSEPR?
Octahedral
AB4E2 MG?
Square planar
Does BrCl have a dipole moment?
Yes; polar (Cl is more electronegative)
Does BF3 have a dipole moment?
No dipole moment; has polar interactions but they cancel out
Does CH2Cl2 have a dipole moment?
Yes!
The closer electrons are too each other the ____ the potential energy would be?
Lower (but then it spikes up after)
Why do we use hybridization to describe compounds?
To describe an overlap of hybrid orbitals and consider bond types in an atom (which VSEPR and molecular geometry do not consider)
What type of hybridization is associated with 2 (# lone pairs + # of bonded atoms)?
sp hybridization
What type of hybridization is associated with 3 (# lone pairs + # of bonded atoms)?
sp2 hybridization
What type of hybridization is associated with 4 (# lone pairs + # of bonded atoms)?
sp3 hybridization
What type of hybridization is associated with 5 (# lone pairs + # of bonded atoms)?
sp3d hybridization
What type of hybridization is associated with 6 (# lone pairs + # of bonded atoms)?
sp3d2
CH4 has which hybridization type?
sp3
BeH2 has which hybridization type?
sp hybridization
PF3 hybridization?
sp3 hybridization
A single bond consists of ____ bond.
1 sigma bond
A double bond consists of ____ bonds.
1 sigma bond and 1 pi bond
A triple bond consists of ___ bonds.
1 sigma and 2 pi bonds
Molecular Orbital Configuration?
Draw from bottom up following orbital rules
How to calculate bond order of MO Configurations?
1/2 (# of electrons in bonding MOs - # of electrons in anti-bonding MOs)
Bond Enthalpy
Manipulate the 3 enthalpies, make your final lewis structure to see how many bonds need to be broken, and divide the enthalpy total by number of bonds broken
What kind of atoms in a lewis structure will form delocalized molecular orbitals?
Atoms that are prone to resonance structures (ie. between two oxygen bonds)
What is the difference between bonding and antibonding molecular orbitals?
Bonding - lower energy, more stable
Antibonding - higher energy, less stable
When creating molecular orbitals, you always want to fill the ____ energy orbitals first.
Lower