CHEM 0310 Lecture 1: Chapter 1

42 views3 pages
6 Feb 2017

For unlimited access to Class Notes, a Class+ subscription is required.

Chapter 1: Structure and Bonding in Organic Molecules
Coulombic Attraction
-The nuclei in a compound are held together by the electrons located between them
-Coulo’s la: opposite hages attat eah othe ith a foe iesely popotioal to the suae of
the distance between the centers of the charges
-All chemical bonding involves the electrostatic attraction between the nuclei of atoms and the
neighboring electrons
-Attracting force = 
-The attractive forces between the neutral atoms causes
energy to be released (bond strength)
-When the atoms reach a certain closeness, no more energy
is released and the distance between them now is called
bond length; after this distance is reached, energy increases
-In covalent bonds: when the nuclei are the appropriate
bond length apart, the electrons are spread out around
both nuclei and the attractive/repulsive forces balance for
maximum bonding
-In ionic bonding: alternative mode of bonding that deals
with complete electron transfer and results in two ions
whose opposite charges attract each other
Ionic/Covalent Bonding
-Covalent bonds are formed by the sharing of electrons while an ionic bond is based on the electrostatic
attraction of two ions with opposite charges
-Atoms tend to form molecules in such a way as to reach an octet in the outer electron shell and obtain
noble gas configuration
-In pure ionic bonding, both reaction bonding partners attain noble gas character with their e- transfers
-The hydrogen atom is unique because it may either lose or accept an electron (proton or hydride ion)
-Covalent bonding shares with single (2e), double (4e), and triple (6e) bonds to gain noble gas
-The sharing of electrons and coulombic attraction contribute to the stability of a bond
-In most organic bonds, the electrons are not shared equally and result in a bond that is in between
covalent and ionic bonding: polar covalent
-The separation of opposite charges is called an electric dipole, symbolized by an arrow pointing from
positive to negative
-In symmetric structures, the polarization of the individual bonds may cancel and lead to molecules with
no net polarization (CO2, CCl4)
-The more electronegative atom is partially negatively charges and has the end of the arrow
Lewis Structures
-These structures are important for predicting geometry and polarity
-Determine the total number of valence electrons, draw the structure, and assign formal charges
-Formal charge = (# of valence electrons) (#of lone pair electrons) (1/2 # of bonding electrons)
-In molecules, charge is not localized on one atom but distributed to varying degrees over its
Resonance Structures
-Resonance structure is a way of describing delocalized electrons within certain molecules or polyatomic
ions where the bonding cannot be expressed by one single Lewis structure
find more resources at
find more resources at
Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

Get access

$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class