CHM138 Term Test 1 Notes
Electron Configuration Rules:
Aufbau Principle: lowest-energy orbitals fill up first. The addition of an electron is
always placed on the lowest possible energy orbital.
Pauli Exclusion Principle: No two electrons in a same atom have identical
electron configuration. Electrons spins in opposite orientation, and .
Hund’s rule: Electron always half-fill all the orbitals in a energy level before fully
fill the orbitals.
Carbon: sp3, tetravalent (tetrahedral structre), 109.5
sp2, trivalent (trigonal planar), 1 p orbital, 120
sp, linear, 2 p orbitals, 180
Carbocation: sp2, no lone pair, valence electron: 3
Carboanion: sp3, 1 lone pair, valence electron: 5
Nitrogen: sp3, trivalent, 1 lone pair, 109.5 Oxygen: sp3, divalent, 2 lone pair, 109.5
Sulfur: sp3, divalent, 2 lone pair, 109.5
Phosphorous: sp3, tetravalent * could have hybridization involving d orbitals, and also
expand octect valence
**Note: Any heteroatom next to a sp2 hybridized carbon is also sp2
Types of Bonding:
Single (sigma)bond: hybridized spn bonds overlap
Double bond: hybridized spn bond + 1 pi bond
Triple bond: sigma bond +2 pi bonds
Chemical Formula To Actual Compound Structure
Saturated form general formula: CnH2n+2
Degree of Unsaturation:
(Saturated # of Hydrogen – Actual # of Hydrogen)/2
Happens when double bonds and ring structures appear in molecules
Degree of Unsaturation – 1 when double bonds or ring appears. It is true
regardless of whether the molecule is pure hydrocarbon or not.
Drawing All Possible Arrangements:
1.Create constitutional isomers
Ex. Propane to isopropane, butane to sec, iso or tert-butane
2.Make rings if # of carbon is sufficient
3.Make double bonds or make rings to satisfy the degree of unsaturation.
4.Break up the long substituent chains or build longer substituent chains
Ex. Ethyl chain break down to 2 methyl chains, hexane becomes 2,3-dimethyl
5.Switch the location of substituent chains
6.Create cis or trans or E, Z stereoisomers
High-electronegative atoms: electron-withdrawing
Low-electronegative atoms: electron-donating
Inductive Effect: The change in electron density in response to the difference in
Net dipole: Net molecular polarity measured by a quantity, dipole moment, u. u =
Formal Charge: A conventional way of assigning a charge on an atom in the
molecule, DOES NOT represent the actual ionic charge. FC is calculated by
“total valence electrons of the free atom” – “# of bonds the atom is involved” – “#
of lone pair”
**Note: DO NOT CONFUSE the concept of polarity with formal charge
Resonance Form: Many possible molecular structure of a single molecule
Resonance Hybrid: The total resultant structure of each resonance form, more
stable than any individual resonance form.
Drawing Resonance Structure Rules:
1.Atom itself can’t not move, only electrons move.
2.Total charge of the molecule can’t change.
3.Resonance structure involves only the replacement of p bonds and lone pair
electrons, no electrons are ever removed or added to an atom.
4.Resonance structure OBEY the rule of valency: atom can only have 8 electrons in
5.Different resonance structures don’t have to be equivalent. If they are different,
the more stable structure resembles more the actual structure of the molecule.
6.A negative charge is stabilized when the more electronegative atom takes the
negative charge, and vice versa with the case of a positive charge.
Bronsted-Lowry Acids and Base are molecules that donates(acid) or
accepts(base) H+ ions.
Lewis Acids and Bases are molecules that accepts an electron pair(acid) or
donates an electron pair(base).
Molecules with an H attached to an electronegative O can be considered as an
Ex. Molecules having –OH (alcohol) –O=C-C-H (ketone) –O=C-O-H (carboxylic
Molecules with an atom having one or more lone pair electrons can be considered as
an organic base.
Ex. Molecules with N: :O: :S: etc.
**Many ionic compounds such as AlCl3 , BH3, TiCl4 etc. are considered Lewis acids.
Predicting acid/base reactions:
SMALLER the pKa, STRONGER the acid, WEAKER the base.
Reaction will only occur when the entities in the reactions are as follow:
Strong Acid + Strong Base Weak conjugate base + Weak conjugate acid
Reaction will NOT occur when:
Strong Base + Weak Acid Weak conjugate acid + STRONGER conjugate
The addition of an electron is always placed on the lowest possible energy orbital. Pauli exclusion principle: no two electrons in a same atom have identical electron configuration. Electrons spins in opposite orientation, and . Hund"s rule: electron always half-fill all the orbitals in a energy level before fully fill the orbitals. Carbon: sp3, tetravalent (tetrahedral structre), 109. 5 sp2, t rivalent (trigonal planar), 1 p orbital, 120 sp, linear, 2 p orbitals, 180. Carbocation: sp2, no lone pair, valence electron: 3. Carboanion: sp3, 1 lone pair, valence electron: 5. Nitrogen: sp3, t rivalent, 1 lone pair, 109. 5 oxygen: sp3, divalent, 2 lone pair, 109. 5. Phosphorous: sp3, tetravalent * could have hybridization involving d orbitals, and also expand octect valence. **note: any heteroatom next to a sp2 hybridized carbon is also sp2 hybridized. Double bond: hybridized spn bond + 1 pi bond. Degree of unsaturation: (saturated # of hydrogen actual # of hydrogen)/2.