Atomic and Molecular Structure

Vitalism

Organic as living or alive, inorganic as a non-living thing

“Important” elements for o chem

C, N, O, P, S, H, F, Cl, Br, I

Electron charge

-1

Neutron charge

0

Proton charge

+1

Valence e-

outermost shell

What are responsible for bond formation

valence e-

Periodic table columns

groups

Periodic table rows

periods

Atomic radius ___ as you go down a group

increases

Atomic radius ___ as you go across periods

decreases

Bond

sharing of e- between 2 atoms

Ionic bonds are between

metal and nonmetal

Ionic bond

transfer of e-, form both positively and negatively charged species

Covalent bonds are between

2 nonmetals or metalloid and nonmetal

Covalent bonds

sharing of e-

Covalent bonds occur between elements of ____ EN

similar

EN difference < 0.5

nonpolar covalent

EN difference of 0.5 — 1.7

polar covalent

EN difference > 1.7

ionic

Dipole moment points towards the ____ EN element in a bond

more

For lewis structures, group # =

number of valence e-

Texas Carbon

5 bonds to a Carbon — NEVER DO THIS

1 val e- = ___ bond(s)

1

3 val e- = ___ bond(s)

3

4 val e- = ___ bond(s)

4

5 val e- = ___ bond(s)

3

6 val e- = ___ bond(s)

2

7 val e- = ___ bond(s)

1

8 val e- = ___ bond(s)

no

Lewis structure arrangement

C, N, O in middle

H, F, Cl, Br, I in periphery

2nd row elements can have no more than ____ valence e-

8

Negative charge

more e-

Positive charge

less e-

Formal charge =

val e- — number of bonds — lone pairs

F, O, N — add bonds

positive formal charge

F, O, N — subtract bonds

negative formal charge

Difference between lewis and kekule

lewis has lone pairs, kekule does not

Condensed structure

omit drawn bonds — just written

Skeletal structures

omit H on Carbons

bond angles represented

C at vertices

Alternate up and down for bond angles

Heteroatoms

molecules with any atom that isn’t C or H

Must draw heteros explicitly

Condensed structure common sequence

1. each non-hydrogen atom identified is followed by the number of hydrogen atoms

2. adjacent non-hydrogen atoms are interpreted as being covalently bonded

Condensed to lewis

1. identify non-hydrogen atoms — how many are bonded together?

2. how many H are bonded to each non-H?

3. how can we add bonds and lone pairs to maximize octets?

For skeletal — try to draw bonds as ___ as possible

far away

Triple bond angle

180

For skeletal structures, triple bonds are drawn as

straight line

Formal Charge =

(number valence e-) — (number bonds) — (total number of non-bonding e-)

Typical Fc’s in o chem

-1, 0, +1

Carbocation has ___ formal charge, ____ an octet, have an open _____, and are ____ hybridized

+1, lacks, p-orbital, sp²

Carbanion have ____ on C, ____ in an sp³ orbital, and are ___ hybridized

lone pair, lone pair, sp³

Resonance

electron delocalization

In resonance, e- spread over multiple atoms in a system of ____ bonds

pi (double or triple)

Double bond has ___ sigma and ___ pi bonds

1, 1

Triple bond has ___ sigma and __ pi bonds

1, 2

Hybrid structures use ____ to show e- spread

dash line

Major resonance structure

looks most like the hybrid

Minor resonance structure

gives information about a molecule’s reactivity