Transcript Chapter 07 and 08 Chemical Bonding and Molecular

Chapter 07 and 08
Chemical Bonding
and
Molecular
Structure
Compound
• Pure substance
• Made of 2 or more elements in a definite
proportion by mass
• Physically and chemically different from
the elements that make up the compound
• All elements (except Noble gases) react to
gain a stable octet. (duet-for H through B)
• Compounds form to gain a stable valence
shell which is LOWER IN ENERGY than
the atoms before the reaction
Ionic compounds
• Metal gives all valence electrons to a
nonmetal or semimetal.
• Both gain stable octets or duets.
• Ionic bond forms due to electrostatic
attraction of cation(s) and anion(s)
• One unit is the lowest whole number ratio
between the cation and anion. This unit is
called a FORMULA UNIT
Covalent Compounds
• Formed when 2 or more nonmetals or a
nonmetal and semimetal SHARE valence
electrons in order to gain a stable octet.
• Tendency for atoms to obtain a stable
octet is called the OCTET RULE.
Part 01
Ionic
Bonding
1. Draw the electron dot (Lewis) Dot
Diagram for the ionic compound
formed between sodium and fluorine.
Na
F
Atom
Atom
d
Sodium must lose its one valence electron to
get a stable octet.
Fluorine must gain one electron to get a
stable octet.
The electron transfer is from sodium to
fluorine and is always from metal to
nonmetal.
[Na] [ F ]
1+
Cation
1-
d
Anion
This is an ionic compound because it
contains a metal cation and a nonmetal
anion. Both ions have a stable octet.
The stable octet is NEVER shown on the
cation; it is ALWAYS shown on the anion.
[Na] [ F ]
1+
Cation
1-
d
Anion
This is a very stable compound. The
positive and negative ions exerts a
strong electrostatic attraction on each
other and bond the ions together.
[Na] [ F ]
1+
Cation
1-
d
Anion
The overall charge of the compound is
zero because 1+ and 1- sums to zero. The
overall charge must always be zero which
shows that the number of electrons lost
is equal to the number of electrons
gained.
[Na] [ F ]
1+
Cation
1-
d
Anion
Electron Dot or Lewis Dot Diagram
Binary Ionic Salt
Binary: Two Elements
Ionic: Metal and Nonmetal
Salt: Metal and Nonmetal
[Na] [ F ]
1+
Cation
1-
d
Anion
Electron Dot or Lewis Dot Diagram
Formula
Shorthand method
of representing a
compound
1+
1-
Na F ALWAYS
Metal on left
Nonmetal on right
Positive on left
Negative on right
[Na] [ F ]
1+
Cation
1-
d
Anion
Electron Dot or Lewis Dot Diagram
Name
Sodium Fluoride
Names of all binary
compounds end in –ide.
2. Draw the electron dot (Lewis) Dot
Diagram for the ionic compound
formed
between
calcium
and
chlorine.
Ca
Cl
Atom
Atom
Calcium must lose its TWO valence
electrons to get a stable octet.
Chlorine must gain one electron to get a
stable octet.
The electron transfer is from calcium to
chlorine and is always from metal to
nonmetal.
Cl
Ca
Cl
This is an ionic compound because it
contains a metal cation and a nonmetal
anion. Both ions have a stable octet.
The stable octet is NEVER shown on the
cation; it is ALWAYS shown on the anion.
1-
1-
2+
[ Cl ] [Ca] [ Cl ]
Anion
Cation
Anion
This is a very stable compound. The
positive and negative ions exerts a
strong electrostatic attraction on each
other and bond the ions together.
1-
1-
2+
[ Cl ] [Ca] [ Cl ]
Anion
Cation
Anion
The overall charge of the compound is
zero because 2+ and 1- and 1- sums to
zero. The overall charge must always be
zero which shows that the number of
electrons lost is equal to the number of
electrons gained.
1-
1-
2+
[ Cl ] [Ca] [ Cl ]
Anion
Cation
Anion
Electron Dot or Lewis Dot Diagram
Binary Ionic Salt
Binary: Two Elements
Ionic: Metal and Nonmetal
Salt: Metal and Nonmetal
1-
1-
2+
[ Cl ] [Ca] [ Cl ]
Anion
Cation
Anion
Electron Dot or Lewis Dot Diagram
Formula
Shorthand method
of representing a
compound
2+
1-
Ca Cl 2 ALWAYS
Metal on left
Nonmetal on right
Positive on left
Negative on right
3.Draw the electron dot
diagram for the ionic
compound formed
between potassium and
oxygen.
K
O
Atom
Atom
d
Potassium must lose its one valence
electron to get a stable octet.
Oxygen must gain two electrons to
get a stable octet.
The electron transfer is from
potassium to oxygen.
K
O
d
This does not represent the
formation of a compound.
Oxygen does not have
a stable octet because it has
not gained two electrons.
A stable compound can
form if a second potassium
atom loses its one valence
electron to the oxygen.
K
K O
d
[K]
1+
[K] [ O ]
1+
2-
d
The name of the compound is
potassium oxide. Its formula is
K21+O2-.
There are two electrons lost
and two electrons gained.
4. Draw the electron
dot diagram for the
ionic compound
formed between iron
and bromine when
iron has three
valence electrons.
Fe
Br
d
Iron must lose its three
valence electron to get a
stable octet. Bromine can
only gain one. The electron
transfer is from iron to
bromine.
Br
d
Fe
Br
d
Br
d
The three electrons are transferred
from the iron to the bromine
when three bromine atoms are
available.
[ Br ] [Fe][ Br ]
d
3+
1-
[ Br ]
1-
d
d
1-
The name of the compound is
iron(III) bromide. The Roman
numeral is inserted after the
name of the metal to indicate the
number of electrons lost and the
oxidation number. This is only
done with elements that can
change their oxidation numbers.
The formula of the compound is
3+
1Fe Cl 3.
Rule: Transition metals and lead
and tin can have variable
oxidation numbers. Therefore a
Roman numeral must be inserted
into the name of the compound to
indicate the number of electrons
lost and the oxidation number of
the metal. Exceptions Ag is
always 1+, Cd and Zn are 2+
What is the formula for:
Calcium Fluoride
Aluminum oxide
2+
Ca
Go to page 73 in notes
2
Al 3+ O 22
Tungsten(IV) Sulfide W
Sodium Carbide
F
1-
3
4+
1+
S
Na C
4
22
4-
What is the name of:
2
2
Mg C
4
Magnesium Carbide
ScF3
Ag2O
Scandium (III) Fluoride
SnS 2
Tin (IV) Sulfide
FrH
Silver Oxide
NO ROMAN numeral!
Francium Hydride
Assignment: p 74-76 (notes)