NH3 4 pairs N is central with 3 single bonds to H

BF3 12 pairs with B central and 3 single bonds; does not obey octet

SF6 24 pairs with S central and 6 single bonds; does not obey octet

SO3 12 pairs with S central and 2 single and one double bond. Resonance

NH4+ 4 pairs with N central and 4 single bonds

SO42- 16 pairs with 4 single bonds

NO2 8.5 pairs, does not obey octet rule

a should be Mg2+, O2- ionic

b should be covalent Cl-O-Cl

c too many electrons should be O=N= O +1

d need 8 electron pairs S=C=N -1 or S-CtripleN -1 (not preferred due to FC)

H- has one lone pair

N 3- has four lone pairs

lithium hydride [Li+], [H-]

calcium hydride [H-], [Ca2+], [H-]

magnesium nitride Mg2+, [N3-],[Mg2+],[N3-], [Mg2+]

a N is bonded to 2 H's and one O FC= O, this is good

If O is bonded to 2 H's and N then N has FC -1 and O has FC +1 not good

b S=C=S FC's=0 Good

C=S=S central S has FC = +2 and C has FC of -2

c O=N-F is best with FC's = o

N=O-F FC of N = -1 and fc of O = +1 no good

d S is the central atom with a double bond to O and two single bonds to Cl

13 pairs of valence electrons

F-S-S-F satisfies octet

S central with double bond to S and 2 singles to F has expanded octet.

a 7 pairs H-O-O-H longest

b 6 pairs O=O shortest

c 9 pairs O-O=O and O=O-O resonance forms with equivalent O-O bonds order 1.5 medium

N is central and forms double bond to O, 2 single bonds to O (2 resonance forms like this)

fc O -1 (terminal single bonded) fc N +1

NO2 has 17 electrons.

The unpaired electrons should form a single bond in the dimer

O-N=O (with N having single electron) can forn N-N bond to bring two molecules together. This is diamagnetic.

Alternatively use O-N=O with single electron on O--molecules would come together to form linear O=N-O-O-N=O molecule. This is OK, but there is experimental evidence for an N-N bond.

S is singly bonded to 4 F's and forms a double bond with C which forms 2 single bonds to H

20 pairs of electrons

NI3 trigonal pyramid 3 e pairs around center

HCN linear 2 pairs around center

SO32- trigonal pyramid 4 pairs around center

NO3 trigonal planar 3 pairs around center

a each N forms single bond to N and O and double to O. Trigonal planar around each N.

Free rotation, molecule not planar.

b linear NtripleC-CtripleN linear about each C

c each C form 4 single bonds, one to C and 3 to H, tetrahedral around each C

d O is central and forms 2 single bonds to C and has two lone pairs. Bent around O.

Each C forms 4 single bonds, one to O and 3 to H. Tetrahedral around C.

13 pairs

S is central forming 3 single bonds and one lone pair, tetrahedral electrons, trigonal pyramid.

a linear, polar , N is negative end

b trigonal planar, S centrral with one double bond to O and two singles. The bonds are polar, but their dipoles cancel so the molecule is not polar.

c linear, bonds polar but cancel, not polar molecule.

d linear, bonds polar and do not cancel, POLAR with O negative end.

e trigonal pyramid, polar bonds, polar, with negative slightly towards O

f tetrahedral, polar bond, molecule not polar.

g tetrahedral, polar bonds and molecule with negative towards F triangle.

O-O breaks (142 kJ/mol) and N-O is made (-222 kJ/mol) so the net DH is -88 kJ/mol.

Data from p. 376 table 11.3.

ICl2+ has 10 e pairs. AX2E2, tetrahedral electron group shape, but bent molecular shape. + on central I.

ICl2- has 11 pairs, -1 on central I, AX2E3, trigonal bipyramid electron pair geometry, linear molecular shape.

resonance!

O-O=O <> O=O-O with +1 FC on cenral O and -1 on singly bonded O. Molecule is bent; each O-O bond is polar, so center is + and ends are -. Net dipole bisects O-O-O angle.