Ch. 7 and 8 Bonding
Valence Electrons = electrons found
in the last occupied shell of an atom
(their “changeable” electrons in their
last shell)
KC3 = It is the same as the “A” group
number
Lewis Dot Structures = shorthand representations of
the chemical symbol and the valence electrons
lose 1 lose 2
lose 3 gain 4 gain 3 gain 2 gain 1
lose 4
+1
+3
+2
+- 4
-3
-2
-1
no change
0
KC 4 = Metals tend to lose electrons and
non-metals tend to gain
KC 5 = Losing electrons, usually a metal
Na  Na+ + ePseudo Noble Gas = when an atom gains
or loses electrons until they have a
full/stable octet (8). They “behave” like
a noble gas.
KC 6 = Anions form by gaining
electrons, usually a non-metal
Cl + e-  ClHalide ion = at atom from the halogen
group that has gained an electron and
become an anion (negative ion)
Section 7.2
Ionic Compound - a compound formed
from the bonding of a cation and an anion
KC 14 = Electrically neutral, the positive
cation and the negative anion cancel each
other out
Ionic Bond - the electrostatic bond that
holds ions together (the “magnetic”
attraction that pulls + and - together)
Chemical Formula - shows the kinds and
numbers of atoms in the smallest
representative unit of that substance
Formula Unit - one “functional piece” of
that substance in lowest whole number
ratio
Magnesium and Chlorine? F? Ca and Cl?
Aluminum and Bromine?
Na and O?
Na and N?
Ca and O?
Ca and N?
Al and S?
Al and N?
The atoms react to cancel
out their charges.
Ionic Properties
Metal and a Nonmetal
Neutral Charge
Strong Intermolecular Attraction
Solid Crystalline Lattice
High Melting/Boiling Points
Liquid form conducts Electricity
Coordination
Numbers
Cesium Chloride
Formula Unit - the lowest
ratio of atoms in an ionic
compound = “one piece”
Jump to Chapter 8
Skip Ch. 7.3
Covalent Bonding Ch. 8
Covalent Bond = An equal SHARING of
valence electrons usually between two or
more nonmetals. (A tug of war between
two elements trying to gain electrons)
Molecule = a particle joined together by
covalent bonds and has no net charge
Molecular compound - composed of
molecules
Diatomic - two atoms covalently bonded
Molecule vs. Formula Unit
A molecule can exist as a single entity (one
piece of a gas).
An ionic compound cannot they are called
“network” solids. Therefore it isn’t an
individual molecule its called a formula unit
KC 1 = Molecular Compounds or Covalent Bonds
usually have low melting and boiling points (already
gases and liquids)
Compare and Contrast Ionic and Covalent/Molecular Properties
Skip to Ch. 8.4
Nonpolar Covalent - electrons shared equally
Polar Covalent - electrons shared, but unequally
KC 32 = The more electronegative (greedy)atom
attracts electrons more strongly and therefore
gains a slight negative charge, the less
electronegative atom gains a slight positive charge
Use the chart to the right to
calculate the difference beteween
the electronegativity values and
determine the bond type.
F = 4.0
4.0 - 1.0 = 3.0
Li = 1.0
Ionic
Ionic vs Polar vs Covalent
Covalent (O2 gas)
Polar (H2O)
Ionic (NaCl)
Share electrons equally
Unequal
Exchange
Gas/Liquid
Liquid
Solid
Low MP and BP
Moderate
High MP + BP
No conducting Electricity
Poor
Good Conductor
Polar
Carbon + Hydrogen
Unequal share
Moderate MP and BP
Liquids and Gases
Moderate Bonds
Poor Conductivity
Poor to moderate
Some overlap
Go back to Ch. 7.3 Metallic Bonding
KC23 = As a “sea” of mobile valence electrons
each metal atom wants to lose, so therefore they
just pass the electrons around between atoms
Metallic Bond = The attraction of the free-floating
valence electrons for the positively charged metal ions
Mobile electrons result in metals that are shiny and
good conductors of heat and electricity, and the lack of
permanent/consistent bonds means they are malleable
and ductile
Contrasted with Ionic bonds which are not malleable
because the bonds are more permanent, and therefore
not malleable, likely to break when struck
KC 24 = very compact and orderly, similar to a ionic crystals
Alloy = a homogenous mixture of 2 or more metals
KC 25 = the properties of alloys are often superior to
the component elements
Sterling silver (Ag and Cu)
Cast Iron (Fe C)
Brass (Cu Zn)
Bronze (Cu Sn)
Stone Age = Flint tools and weapons, Gold discovered, but too soft,
not a good tool/weapon
Copper Age = decent tool/weapon (3800BC Melting Ores, Cu
melting temp relatively low 1083C)
Bronze Age = 2800BC natural alloys of copper and tin, unbelievably
useful, weapons and tools, but mostly for ruling class and armies,
powerful civilizations
Iron Age - 1500BC Iron abundant but relatively high melting point
(1500C) makes hard to work with in primitive forge, literally hammer
out impurities, and reforge (but still not better than Bronze)
Steel Age - 1100BC heating iron in a forge with Charcoal (carbon)
then water quenching = Steel China is melting and casting Iron by
500BC, and this isn’t done in Europe until 1100AD. Wow!!
Electrochemical cell = a device capable of either
deriving electrical energy from chemical reactions, or
facilitating chemical reactions through the introduction
of electrical energy.
A battery is an electrochemical cell. It separates two
types of metal immersed within a strong ionic solution
(electrolyte).
The property for the tendency of metals to exchange
electrons is enhanced when immersed in a strong ionic
solution, that allows the electrons to flow between the two
different metals. This flow of charge is electricity.
The property for the tendency of metals to exchange
electrons is enhanced when immersed in a strong ionic
solution, that allows the electrons to flow between the two
different metals. This flow of charge is electricity
KC 2 = The number and kinds of atoms in a molecule
It doesn’t tell you the STRUCTURE.
Structural Formulas
Shows you the specific arrangement of the
atoms found in a substance
C6H12O6
C6H12O6
Isomers - same numbers and kinds
of atoms but different structures
Models
KC 13 = the configuration of noble gases
Covalent bonds usually contain the “greedy non-metals
Single Covalent Bond  two atoms held
together by a sharing of a pair of electrons
KC 14 shared pairs are dotted in between
Or shown as a dashed line in a Formula
Unshared pairs - pairs of electrons that are not shared
between two atoms
Double Bond = a bond from two shared pairs (4 electrons)
Triple Bond = A bond from three shared pairs (6 electrons)
What is a coordinate covalent bond?
One atoms contributes both shared electrons (its
less greedy than the one it is bonding to)
Give an example of a coordinate covalent bond.
Carbon Monoxide
KC 16 How is a coordinate covalent bond different from
other covalent bonds?
The shared pair of electrons comes from one atom,
not one from each
What is a polyatomic ion?
A tightly bound group of atoms that has a charge,
and yet behaves as a unit (package)
What is bond dissociation energy?
Energy required to break a covalent bond between
two atoms (Ex: H2 molecule = 435kJ/mol)
KC 17 How is the strength of a covalent bond related to
its bond dissociation energy?
A large bond dissociation energy corresponds to a
strong covalent bond.
Explain this idea in terms of carbon compounds, like
methane and coal, and their relative stability.
Carbon and Hydrogen are equally strong in their
pull, and therefore hard to separate = stable
Bond Dissociation Energies
KC 18 Draw the electron dot structure resonance structures of
ozone and explain how they describe its bonding.
Ozone is a hybrid, or mixture of the extremes of the
resonance forms
What are resonance structures?
A structure that occurs when it is possible to draw two or
more valid electron dot structures
KC 19 List three ways in which the octet rule can sometimes
fail to be obeyed.
Cannot be satisfied in molecules whose total number of
valence electrons is an odd number, there are also molecules
in which an atoms has fewer, or more, than a complete octet
(like NO2 page 228)
Draw the electron dot structure for sulfur hexafluoride. What is
the unique application of sulfur hexafluoride.
Page 229
Sigma Bond = two atomic orbitals combine to form a molecular
orbital that is symmetrical around the axis connecting the 2 nuclei
Pi Bond = the bonding electrons are found in sausage
shaped regions above and below the bond axis
What is VSEPR theory?
Valence Shell Electron Pair Repulsion Theory
KC 24 Explain how the VSEPR Theory can be sued to
predict he shapes of molecules.
Repulsion between electron pairs causes
molecular shapes to adjust so the valenceelectron pairs stay as far apart as possible
3
4
5
6
7
Each bond counts as an area
that shapes the molecule.
So does each set of unpaired
electrons.
KC 34 Compare the strengths of intermolecular attractions to
the strengths of ionic bonds and covalent bonds.
Weaker than ionic or covalent bonds
What are van der Waals forces?
Two weakest molecular attractions caused by dipole
interactions and dispersions
What are dipole interactions?
Polar molecules attracted to one another
What are dispersion forces?
The weakest force caused by the motion of electrons in
a non-polar molecule from one side of the molecule to
the other creating temporary dipole charges
What are hydrogen bonds?
A specific type of dipole interaction when attractive
forces in which a hydrogen covalently bonded to a very
electronegative atom is also weakly bonded to an
unshared pair of another electronegative atom
How does hydrogen bonding affect water?
Surface tension
How does hydrogen bonding affect the structure of DNA?
Attraction across the 2 different helixes, or base pairing
is due to Hydrogen bonding