CHM 1100 E2 Crash Course

Lewis structure: first step?

Count total valence electrons; add e- for negative charge, subtract for positive charge.

Formal charge formula?

FC = valence e- - nonbonding e- - 1/2(bonding e-).

What makes the best resonance structure?

Fewer/smaller formal charges; negative charge preferably on the more electronegative atom.

Which period-2 atoms cannot exceed an octet?

C, N, O, F (and Ne).

Bond polarity depends mainly on what?

Electronegativity difference (ΔEN).

What is resonance?

Same atom arrangement, different valid electron/bond placement; actual structure is a resonance hybrid.

Bond order vs bond length/strength?

Higher bond order usually means shorter, stronger bonds.

2 electron groups: geometry and hybridization?

Linear; sp; 180°.

3 electron groups: geometry and hybridization?

Trigonal planar; sp2; 120°.

4 electron groups: geometry and hybridization?

Tetrahedral; sp3; 109.5°.

5 electron groups: geometry and hybridization?

Trigonal bipyramidal; sp3d; 90°, 120°, 180°.

6 electron groups: geometry and hybridization?

Octahedral; sp3d2; 90°.

How do you decide molecular polarity?

Draw Lewis structure → determine shape → ask whether bond dipoles cancel.

SF4 shape and polarity?

Seesaw; polar.

ICl4- shape?

Square planar.

TeCl6 geometry and polarity?

Octahedral electron geometry; octahedral molecular geometry; nonpolar.

Hybridization of a benzene carbon?

sp2.

One s + three p orbitals hybridize into what?

Four sp3 hybrid orbitals.

Sigma vs pi bond counting?

Every bonded pair has 1 sigma; each double adds 1 pi; each triple adds 2 pi.

MO theory: bond order formula?

Bond order = 1/2[(bonding e-) - (antibonding e-)].

What makes a species paramagnetic?

At least one unpaired electron.

MO theory: three tasks emphasized in the review?

Count valence e-; choose correct MO diagram; determine bond order/stability/length/paramagnetism.

Band gap: conductor vs semiconductor vs insulator?

Conductor: tiny/overlap; semiconductor: intermediate; insulator: large.

n-type semiconductor dopant?

Dopant has one MORE valence electron than the host.

p-type semiconductor dopant?

Dopant has one LESS valence electron than the host, creating holes.

What is an alkane / alkene / alkyne?

Alkane: C-C; alkene: C=C; alkyne: C≡C.

What functional group is -CHO?

Aldehyde.

What functional group is -COOH?

Carboxylic acid.

What functional group is -COO- between carbon groups?

Ester.

What functional group is C=O between two carbons?

Ketone.

What functional group is -OH on carbon?

Alcohol.

What class contains benzene rings?

Aromatic compounds.

How do you name an ester?

Alkyl group from the alcohol first, then carboxylate name ending in -oate.

How do you choose the parent chain in IUPAC naming?

Choose the longest chain containing the highest-priority functional group or multiple bond.

What are structural isomers?

Same molecular formula, different atom connectivity.

What are geometric (cis/trans) isomers?

Same connectivity, different arrangement around a restricted bond such as C=C