Bonding 007

Report
How many
valence electrons
do atoms want to
obtain?
A bond is the electrostatic force
of attraction between two particles
(atoms, ions or molecules)
•They are formed/broken
during Chemical Reactions
•Formed = release energy
•Broken = absorb energy
Valence Electrons - want to
achieve happiness
“Octet Rule” - want a full
valence shell = HAPPY!
Ionic
Atoms Involved
- metal and nonmetal
Covalent - nonmetal + nonmetal
Metallic - metal + metal
Find the correct formula for a
compound!!
•Use the oxidation #’s
•Put the positive one first
+1
H
+ O
-2
 H2O
+2
Ca + Br
+2
-1
 CaBr2
-1
Mg + (OH)  Mg(OH)2
+2
Sr
-2

SrO

Sr
O
+ O
2 2
+1
-2
Na + Se  Na2Se
+3
-1
Fe (III) + (HCO3) 
Al
+3
-3
Fe(HCO3)3
Al3(PO4)4)3
+ PO4  Al(PO
Remember: A bond between a
metal and a non-metal atom
The metal keeps its name, and
the non-metal ends in -ide
KBr 
Potassium Bromide
CaCl2  Calcium Chloride
What are the formulas for
the compounds between:
Oxygen and Phosphorus
Iodine and Barium
Speed
Bonding
As pure elements, these seven elements form
molecules containing two atoms
H2
HON – 17
N2
O2 F2
Cl2
Br2
I2
As pure elements, these seven elements form
molecules containing two atoms
HON – 17
Transition
Elements
Atoms combine to form compounds
By bonding atoms together, their properties change
I. Bonding
A.Chemical Bond
H
O
H22O
This is the attractive force between atoms or ions
Results from the rearrangement of valence electrons
B. Energy Changes
As a chemical bond forms, atoms are brought
to a lower energy state
Free atoms have more energy than bonded atoms
As we said before, atoms can bond together by moving
their valence electrons around
Actually, atoms can either lose, gain or share electrons.
This gives us several types of bonds
e- e- e- e- e
+
Ionic Bond Atoms transfer electrons
Creates ions
Forming ions An ion is formed when atoms lose or gain
electrons
Ion =
Charged atom due to a loss or gain of electrons
Binary Ionic Compounds
- change the end of the non-metal to -ide
MgI2  Magnesium Iodide
K2O  Potassium Oxide
CoBr2  Cobalt (II) Bromide
CoBr3  Cobalt (III) Bromide
When you have more than two
elements, refer to Ref. Table E.
NaOH  Sodium Hydroxide
(NH4)(NO2) Ammonium Nitrite
KMnO4  Potassium Permanganate
Ni2(CrO4)3  Nickel (II) chromate
What would the oxidation
number be for Iron in the
following compounds:
Fe2O3
FeS
You must look at the types of atoms and their
electronegativity differences.
Ionic - bond between a metal and a non-metal
Electronegativity difference should be = to or > than 2.0
This means that one atom can pull an e- from another atom
Big Dog vs Little Dog
Results in the formation of ions
Mn + F 
K+O 
1.6 - 4.0
0.8 -
= 2.4
3.4 = 2.6
Metal + nonmetal Ionic bond
•Further apart on the Periodic table
•Greater difference in
Higher
electronegativity
=
ionic character
Higher ionic character
High ionic character
Writing Formulas
Lab
What are the formulas for the
following compounds:
Sodium thiocyanate
Ammonium oxide
Compound Naming Race
Writing Formulas
Lab
What type of bonds are in the
following compounds?
Calcium Bromide
Sulfur Oxide
You must look at the types of atoms and their
electronegativity differences.
Covalent - bond between two non-metals
Electronegativity difference should be less than 2.0
This means that one atom is not able to pull an e- away
Two of the same sized dogs
DOES NOT FORM IONS!!!
C + Cl
 2.6 - 3.2 = 0.6
I + I
 2.7 - 2.7 = 0.0
Covalent - bond between two non-metals
Specific Types
Polar Covalent - the unequal sharing of eElectronegativity differences of 0.5 – 1.9
Fe2O3  1.8 - 3.4 = 1.6
Results in partial charges on the atom
Non-Polar Covalent - the equal sharing of eElectronegativity differences of 0.0 – 0.4
Usually only in diatomic molecules
O2

3.4 -
3.4
= 0.0
Nonmetal + nonmetal
•Covalent bond
•Small difference
in electronegativity
Ternary substance - compound containing polyatomic ion
Polyatomic ion is covalently bonded together
Bond between polyatomic ion and atom is ionic
MgSO4
Results in a
covalent compound having
both IONIC and
Ionic
COVALENT bonds
Metal + Metal
Metallic bond
= sea of electrons
Electrons are free to move all over, not bound to one nucleus
Alloy -
Different metal atoms mixed together
Brass – copper and zinc
Bronze – copper and tin
Gold – Gold, silver, copper
Ionic compounds can also be drawn as Lewis structures.
Positive ion  Cation
Since all the valence electrons are removed, no
valence electrons are shown.
+
The charge is written above
Na
Negative ion  Anion
The added valence electrons indicate a full valence
shell.
Cl
Brackets are added and the charge is written on the outside
Ionic compounds
Write the positive ion next to the negative ion, and
include their charges
+
Na
Cl
Covalent compounds
First write element symbols and then draw their
valance electrons.
H2O
H
H
O
Now move the atoms to pair up any unpaired electrons
H O
H
Give the formula and dot diagram for the compound
formed from the following compound:
CO2
EN difference ?
Give the formula and dot diagram for the
compound formed from the following elements:
Fluorine and Magnesium
EN difference ?
Give the formula and dot diagram for the
compound formed from the following elements:
Strontium and Bromine
EN difference ?
Give the formula and dot diagram for the
compound formed from the following elements:
NH3
EN difference ?
Give the dot diagram for the compound:
Sodium hydroxide
Give the formula and dot diagram for the
compound formed from the following elements.
Phosphorus and Chlorine
δ+
Cl
δ-
Cl P Cl
Cl
Cl
δ-
δ-
Cl
What are they?
•The attractive force between
the hydrogen attached to a
highly electronegative atom of
one molecule and a highly
electronegative atom (N, O, F
only) of a different molecule.
•Only found in polar covalent
compounds
•Individually a very weak bond
Unique properties of water
•Very High M.P. and B.P.
•Less dense as a solid
•High Heat of Vaporization
•Sweating, climate moderation
•High Surface Tension
Fewer molecules to be attracted to therefore a
stronger attraction
Hydrogen bonding is the strongest of the
intermolecular bonds!!!! (click for video)
Bubble Lab
Give the formula and dot diagram for the
compound formed from the following elements:
Strontium and Iodine
+2
Sr I
I
-1
-1
BUBBLES
The Jesus lizard – the Basilisk lizard
scroll down to view movie
Rules are similar to ionic compounds, just need
to add prefixes for the number of atoms
mono2 di1
hexa7 hepta6
tri-
8
tetra5 penta-
9
3
4
octa-
nona10 deca-
Try the following:
CO2
Carbon dioxide
CCl4
Carbon tetrachloride
Dinitrogen monoxide
N2O
Diphosphorus pentoxide
P2O5
Naming
Covalent
Molecules
wkst 1
Physical Properties of CF4 and NH3 at STP
Compound
MP (ºC)
BP (ºC)
Solubility in water @ 20ºC
CF4
-183.6
-127.8
Insoluble
NH3
-77.7
-33.3
Soluble
A.
State evidence that indicates that NH3 has stronger
intermolecular forces of attraction than CF4.
B.
Draw the lewis dot diagram for CF4. Is it a polar or
non-polar molecule
Molecules - are only covalently bonded
Polarity of molecules - completely dependent on the shape of the molecule
- molecules are only polar if they have polar covalent bonds
- if you can draw one straight line and all the (+) are
on one side and all the (-) are on the other side, the
molecule is polar
Dipole
Molecule which has a + side and a - side
A molecule is either polar or non-polar with respect to charge
Assigning + and - to atoms
The atom with the higher electronegativity gets the The atom with the lower electronegativity gets the +
Asymmetrical charge distribution Negative(-) end and Positive(+) end
- results in the formation of a Polar molecule
Symmetrical charge distribution Equal distribution of charge
- results in the formation of a Nonpolar molecule
Examples
-
+
O == C== O
nonpolar
N+
H--Cl
polar
H H H
+
+ +
polar
Molecular
Polarity wkst
Explain, in terms of electrons,
why the bonding in NaCl is ionic?
Dissolve in polar solvents
Dissolve in non-polar solvents
Dissolve in polar solvents
The process where ionic
compounds split (separate)
into their respective ions
A substance containing free
ions that makes the substance
electrically conductive
Draw the Dot Diagrams for the
following compounds and
determine if they are polar or
non-polar, and name them:
H2 O
CH4
Connectors # Needed
Spheres
Black
Sticks
Springs
6
4
You might have to share with
another group to get 4.
Red
Yellow
Green
Blue
# Needed
2
2
4
1
1
III. VSEPR
Class
Shape
AX
Linear
HCl
AX2
Linear
CO2
AX3
Trigonal
Planar
BH3
AX4
Tetrahedral
CH4
: AX3
Pyramidal
NH3
BENT
H2O
..
:AX2
Model
Example
What are the names of the
following compounds:
CoI3
MgSO4
A substance will conduct electricity IF it has freely
moving charged particles Particles can be ions, electrons,
etc. as long as they can move
Metal Conducts electricity in solid or liquid form
Freely moving electrons allows the electricity to flow.
Ionic substance Does NOT conduct in solid form
Ions are locked in place Has charges, but not free moving
Liquid When melted, can conduct electricity
Ions are mobile enough to move past each other
+
+
+ +
+ - + -
Solution In solution, ions separate Dissociate
Ions are free to move, conducts electricity
Covalent
Solid Doesn’t conduct electricity
No charged particles
Liquid Doesn’t conduct electricity
No charged particles
Solution Some types of covalent molecules can be
broken down to make ions
Ionization
Conducts some electricity, because only a few of the
molecules in the sample are broken down


Used to determine a substances properties –
only found in covalently bonded substances
Relatively weak compared to ionic, metallic, and
even covalent bonds
 Examples
forces – for your college education
 Dipole-Dipole forces – again something for college
 Hydrogen bonding – we’ve done these
 Molecule-ion attractions – we’ll look at these
 Dispersion
Molecule-Ion Attractions
– the attraction
between the ions and molecules of water in a solution
A Good Animation
•Hard
Ionic
•Good Conductors
•Not as solids
•High MP & BP
•Dissolve in Polar
Substances - water
Covalent
AKA – Molecular Substances
•Generally soft
•Poor Conductors
•No charged particles
•Low MP & BP
Coordinate Covalent Bond
- one atom donates BOTH electrons that are shared
Hydronium
ion
Ammonium
ion
H O + H
H
+
H N H+ H
H
+
+
H O H
H
H
+
H N H
H
Molecular
Polarity
handout
Lab
Check in
Bonding
Packet
Affect on Boiling Points
Stronger force = Higher Boiling Point
Give the name of a substance
that can NOT conduct
electricity in the solid phase but
can as a liquid. Explain why.
Name the following compounds:
PCl3
K2C2O4
Covalent bonds are classified as single,
double,
or triple bonds depending on the number of
electrons shared between the two nuclei.
Intermolecular Forces
Intermolecular forces are attractive forces between molecules.
Intramolecular forces hold atoms together in a molecule.
Intermolecular vs Intramolecular
•
41 kJ to vaporize 1 mole of water (inter)
•
930 kJ to break all O-H bonds in 1 mole of water (intra)
“Measure” of intermolecular force
Generally,
intermolecular
forces are much
weaker than
intramolecular
forces.
boiling point
melting point
DHvap
DHfus
DHsub
11.2
What are the names of the
following compounds:
KCH3COO
BaCr2O7
11.2
Types of Intermolecular Forces
3. Dipole-Dipole Forces
Attractive forces between polar molecules
Orientation of Polar Molecules in a Solid
11.2
FLORIDA
STATE
Draw the electron dot diagram
for the following :
Magnesium
Iodide ion
1. Barium Sulfite
2. SrS
3. Cesium Selenide
4. KClO3
5. Calcium Sulfide
6. BaCrO4
7. Strontium Fluoride
8. NaNO3
9. Cs(ClO2)
10. Magnesium Oxalate
What types of
chemical bonds
exist?
1. Barium Sulfate
2. CaO
3. Potassium Oxide
4. Na2CO3
5. Magnesium Oxide
6. SrCrO4
7. Barium Chloride
8. NaNO3
9. MgSO4
10. Beryllium Sulfite
Sodium Atom
+11
Chlorine Atom
-11
-10
+1
0
Total charge
a positive ion neutral
Atom is considered
Called a Cation
+17
-17
-18
-1
Total charge 0
a negativeneutral
ion
Atom is considered
Called an Anion
Cation Positive ion due to the loss of electrons
Anion Negative ion due to the gain of electrons
meow.
Examples - Determine the type of ion shown and
explain how it was made from a neutral atom.
Ion
K+
Type of Ion
cation
How it was made
Lost 1 electron
Ca+2
cation
Lost 2 electrons
O-2
anion
Gained 2 electrons
Br-
anion
Gained 1 electron
Draw the electron dot formula for neutral atoms of Na and F
+
Na
F
All atoms want a full octet in their valence shell. This is a
stable configuration. When ionic bonding occurs,the one
valence electron in Na is transferred to F
Notice how both atoms have a full octet?
F has gained an electron to get a total of 8.
Na uses its full shell underneath as a full valence
Na
2
8
The attraction between the + and - ion causes the bond
Review Ionic bonds
1. Electrons are transferred
2. Ions are created Cation lost e-, anion gained e3. Very strong bond. Has high melting and boiling
points, and a very rigid structure
4. Creates ionic substances
1
+
Covalent Bonds
a. Electrons in bonds
- No transfer of electrons
- Electrons are shared between valence shell of atoms
- Weaker bonds than ionic
In covalent bonding, atoms get a
full octet by sharing electrons
between their valence shells
Hydrogen and helium do not need 8 electrons, only 2
H
H
So the molecule H2 looks like
H H
In covalent bonding, atoms still want to achieve a
noble gas configuration
The octet rule
But rather than losing or gaining electrons, atoms now share an
electron pair.
The shared electron pair
is called a bonding pair
Look at the parts of H2O
H
O
This indicates that H2O looks like
O
H
H
H
H---O
|
H
Not H--O--H
Or H--H--O
Review
In a covalent bond, electrons are shared between valence shells
There is NO transfer of electrons, so no ions are formed
Their bonds are weaker, have lower melting and boiling points
If atoms are covalently bonded, they make

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