3. Bonding

Question 1

Exceptions to octet rule

Answer 1

H, He, Li, Be, B

Within or after period 3

Question 2

Does a molec with polar bond always polar?

Answer 2

Nope, depends on cancelled out dipole moments

Question 3

London dispersion forces

Answer 3

When a covalent bond contains slight unequal sharing of e- leading to constant polarization and counter polarization; type of van der Waals force; weakest of intermolecular forces
LDF = only intermolecular force in noble gases, but LDF = present in ALL molec. LDF inc with bigger atoms b/c they have more e- to interact —> more polarizable

Question 4

Ionic bonding vs covalent bonding vs coordinate covalent bonding vs heterolytic rxns

Answer 4

When 1+ e- of atom with low IE = transferred to atom with high EA; from crystal lattice - large, organized arrays of ions vs when e- pair = shared b/w atoms with similar electronegativity; if pair = shared unequally —> polar vs when shared e- = contributed by only one of two atoms (ex: when Lewis base gives e- pair to Lewis acid) vs opposite of coordinate covalent bonding: bond breaks and both e- go back to one of the products

Question 5

Bond energy vs bond dissociation energy/bond enthalpy

Answer 5

AVG ENERGY required to break all bonds into isolated, gaseous states; the more e- shared —> the more energy needed to break it
The higher the bond energy —> the shorter the bond length (ex: triple bonds vs double bonds) vs THE ENERGY IT TAKES TO BREAK A SPECIFIC BOND IN A GAS PHASE; always pos b/c it requires energy

Question 6

Know which bond is strongest b/w triple, double, single, sigma and pi bonds. Why is single bond stronger than sigma bonds?

Answer 6

I pretty much laid it out for you. S orbitals have more overlap than p orbitals

Question 7

How to find formal charge? How to find valence e-?

Answer 7

# ve- in free atom minus # of ve- in bonded atom
Group # on periodic table

Question 8

Linear vs trigonal planar vs tetrahedral vs square planar vs trigonal bipyramidal vs octahedral angles and hybridization

Answer 8

180; sp vs 120; sp2 vs 109.5; sp3 vs 90; sp3d2 90,120,180; sp3d vs 90, 180; sp3d2, 6 sigma bonds and no lone pairs

Question 8

Valence shell electron pair repulsion theory (VSEPR)

Answer 8

3D arrangement of atoms around a central atom is determined by repulsions b/w bonding and nonbonding e- pairs in valence shell of central atom

Question 9

Electronic vs molecular geometry

Answer 9

Position of all bonding and lone e- pairs around central atom vs position of only bonding e- pair; uses coordination number - # of atoms that surround and bonded to central atom

Question 10

Molecular orbital vs bonding orbital vs antibonding orbital

Answer 10

When 2 atoms form a cmpd —> atomic orbitals interact => molecular orbital vs signs of 2 atomic orbitals that are same vs 2 atomic orbitals that are different

Question 11

Sigma bond vs pi bond

Answer 11

single bonds; head to head overlap, allows free rotation around axis vs double and triple bonds; parallel e- clouds overlap, doesn’t allow free rotation around axis

Question 12

Which elements do H bonds?

Answer 12

F, O, N; H bonds = strongest type of dipole dipole interaction

Question 13

How to determine higher bpts based on intermolecular forces?

Answer 13

Consider all the forces involved (dispersion forces, dipole-dipole, H bonds): Ionic bond = strongest, dispersion forces = weakest; if molec have 1+ type of forces —> higher bpt

Question 14

How to determine largest dipole moment?

Answer 14

If linear and no dipoles cancel out —> strongest dipole moment. If bent or some dipoles cancel out —> weaker dipole moment

Question 15

What is a conjugated system?

Answer 15

Alternating single bonds and multiple bonds; this allows pi e- to delocalized throughout unhybridized p orbitals or heteroatoms with lone pairs of e-

Question 16

S orbital vs p orbital vs node

Answer 16

Round and spherical, centered around nucleus vs 2 lobes located symmetrically around nucleus (like a dumbbell) vs area where probability of finding e- = zero (ie. At the nucleus)

Question 17

Induction

Answer 17

Refers to distribution of charge across sigma bonds. Electronegative atoms like more e- around them —> more neg (this less electronegative atoms = more pos)

Question 18

Hybrid orbitals vs sp3 vs sp2 vs sp orbitals

Answer 18

Formed by mixing diff types of orbitals vs 1 s orbital + 3 p orbitals = 4 sp3 orbitals, done by putting 1 2s e- into the last unoccupied p space, mostly tetrahedral vs 1 s orbital + 2 p orbitals = 3 sp2 orbitals, alkenes, 120 degrees apart —> max repulsion vs 1 s orbital + p orbital = 2 sp orbitals, alkynes, 180 degrees apart —> linear

Question 19

How to find dipole moment mathematically?

Answer 19

p = q*d

p=dipole moment
q=charge
d=displacement vector b/w 2 partial charges

Question 20

Exceptions to e- config

Answer 20

4th and 9th column of transition metals can be half filled (ex: 4s13d5 or 4s13d10 as opposed to 4s23d4 or 4s23d9). These exceptions basically have same stability as regular stable e- configs

Question 21

Crystalline lattice

Answer 21

Repeating pos and neg ions in a solid state

Question 22

Why is temp necessary for phase change?

Answer 22

To overcome intermolecular forces