exam two

Question 1

practice lewis structures

Question 2

practice resonance structures

Answer 2

where there are two or more valid lewis structures of a molecule
> arrangement of electrons are different but the atomic value / formal charges are the same

Question 3

exceptions to the octet rule

Answer 3

1st row e-‘s can not exceed 2 shared e-‘s

2nd row cannot exceed 8 shared e-‘s

3rd row can exceed 8 shared e-‘s

boron can have incomplete octet’s

Question 4

what are formal charges

Answer 4

valence e-‘s [minus] # of dots (lone pairs / unshared e-‘s) [minus] # of bonds (half of the bonded e-‘s)

ideally want zero formal charges or equal to the ion’s charge

Question 5

VSPER theory - practice structures and traits + shapes

Answer 5

shapes -

linear: two e- (bonding) groups; 180°

trigonal planer (flat): three e- groups = 120°
> if two bonding groups + one lone pair has BENT molecular geometry (<120°)

tetrahedral: four e- groups = 109.5°
> if one lone pair molecular geometry is TRIGONAL PYRAMIDAL (<109.5)
> if two long pairs molecular geometry is BENT (<109.5)

trigonal bipyramidal: five e- groups = 120° equatorial, 90° axial
> if one lone pair molecular geometry is SEESAW (<120° equatorial, <90° axial)
> if two lone pairs molecular geometry is T-SHAPED (<90°)
> if three lone pairs molecular geometry is LINEAR (180°)

octahedral: six e- groups = 90°
> if one long pair molecular geometry is SQUARE PYRAMIDAL (<90°)
> if two lone pairs molecular geometry is SQUARE PLANER (90°)

Question 6

inter vs. intramolecular forces

Answer 6

intra = within (the ‘r’ is WITHIN the prefix
> INTRAmolecular forces hold atoms together

inter = between or among (the ‘r’ is BETWEEN the prefix and the rest of the word)
> INTERmolecular forces are interactions between molecules

Question 7

trends of electronegativity; order strongest to weakest + where they’re present

Answer 7

electrostatic forces: present in ions / ionic compounds (+ -)

ion-dipole: mixture of ionic and polar compounds (+ surrounded by partial -‘s; vice versa)

h-bonding: FON; acceptors and donors

dipole-dipole: present in polar molecules (partial - to a partial +; vice versa)

london dispersion (LDF’s): present in all