CHEM 112 Chapter Notes - Chapter 10.1-10.4: Chemical Polarity, Coordinate Covalent Bond, Electric Potential
by OC1369806
This preview shows half of the first page. to view the full 3 pages of the document.
Chemistry Week 4
10-1
Lewis theory
1. Electrons, especially valence electrons, play a fundamental role in chemical bonding
2. In some cases, electrons are transferred from one atom to another; these are ionic bonds
3. In other cases, electrons are shared between atoms; these are covalent bonds
4. Electrons are transferred or shared in such a way that each atom acquires a stable electron configuration. Usually this is a noble gas
configuration with 8 outer shell electrons or an octet
Lewis symbols and Lewis structures
o A Lewis symbol consists of the chemical symbol to represent the nucleus and core electrons of an atom , together with dots places
around the symbol to represent the valence electrons
o A Lewis structure is a combination of Lewis symbols that represents either the transfer or sharing in a chemical bond
Lewis structures for ionic compounds
o No bond is 100% ionic
o Both the charges of the anion and the cation are shown
10-2
Covalent bonding
Octet rule - a requirement of 8 valence electrons
Single covalent bond - the sharing of a single pair of electrons between bonded atoms
Bond pair – applies to a pair of electrons in a covalent bond
Lone pair – applies to the pairs of electrons that are not involved in bonding
Coordinate covalent bond
o A covalent bond in which a single atom contributes both of the electrons to a shared pair
Multiple covalent bonds
o Double covalent bond – bonded atoms share two pairs of
electrons between them
o Triple covalent bond – bonded atoms share three pairs of
electrons between them
10-3
Polar covalent bonds and electrostatic potential maps
A covalent bond in which electrons are not shared equally between two atoms is a polar covalent bond
Electrons are displaced towards the more nonmetallic element
The more nonmetallic element is signified with a �− and the more metallic element is signified with a �+
o Called potential charge
Electrostatic potential map – a way to visualize the charge distribution
The electrostatic potential is the work done in moving a unit of positive charge at a constant speed from one molecule to another
o Obtained by hypothetically probing an electron density surface with a positive point charge
o When positive point charge is attracted to an electron rich region, electrostatic potential is negative
o When positive point charge is attracted to an electron weak region, electrostatic potential is positive
o For a neutral atom if the potential at a point is positive then it is likely that the molecule has a net positive charge
o Red is low energy and most negative electrostatic potential of the spectrum and blue is the most positive electrostatic
find more resources at oneclass.com
find more resources at oneclass.com
You're Reading a Preview
Unlock to view full version