Most basic form of representing molecular structures.

Rules to forming LDS:

1) find total # of ve's for all atoms in molecule

2) use one pair of e's to form one bond between each atom

3) arrange remaining e's around the atoms to satisfy the duet rule for H and

    the octet rule for other atoms

Exceptions:

1) compounds with B or Be may contain less than an octet

2) Molecules with an atom containing more than an octet MUST contain an

    atom from the 3rd period or greater in the PT (d orbitals)

does not show bonds

CH3CH2CH2OH

black wedge = coming out of page

dashed wedge = going into page

lines = in plane of page

indicates #s of pairs of Hs a compound requires to be a saturated alkane

2n + 2 hydrogens (n = # of Cs)

Index of H deficiency =((2n + 2) - (# Hs in cmpd))/2

* Count halogens as Hs

Ignore O atoms

Count N as 1/2 H

Prefix            # of Cs

meth-                1

eth-                   2

prop-                 3 

but-                   4

pent-                 5

hex-                  6

sept-                 7

oct-                   8

non-                  9

dec-                  10

Bonding

1) forms when the bonding pair of e's are localized directly between the two

    bonding atoms

2) have the lowest E and are most stable form of covalent bonding

3) strong

1) an additional bond formed between 2 σ-bonded atoms

2) orbitals form above and below the σ-bonding e's (double bond)

3) orbitals form on the sides of the σ-bonding e's (triple bond)

4) independently weaker than σ-bond (less E required to break the bond)

5) nevertheless, they strengthen overall bond b/t atoms, shorten the bond

    length, and increase bond E

6) e's are further from nucleus than those in σ-bond, thus they are at a

    higher E level, are less stable, and are more reactive

7) 3rd row elements form weaker ∏ bonds than 2nd row elements

8) only C, N, O, and S commonly form double and triple bonds

9) ∏ bonds prevent rotation

combined orbitals that create new shapes and E levels:

Hybridization        Bond angles                                 Shape

       sp                  180                                  linear

       sp²                     120                            trigonal planar

       sp³                   109.5                   tetrahedral; pyramidal; bent

     dsp³                 90; 120      trigonal-bypyramidal; seesaw; t-shaped; linear

   d²sp³                 90           Octahedral, square pyramidal; square planar

*shape differences depend upon # and location of LPe's