Transcript Chemical Bonding & Reactions

1
Adventures
of Oxygen
Clip
2
GOALS
1. Compare & contrast ionic and covalent bonds in terms of
electron position.
2. Predict formulas for stable binary ionic compounds
based on balance of charges.
3. Determine the Types of ions formed by representative
elements
3. Use IUPAC nomenclature for transition between chemical
names and chemical formulas of
- binary ionic compounds
- binary covalent compounds
4. Apply the Law of Conservation of Matter by balancing
the following types of chemical equations:
• Synthesis
• Decomposition
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16
• Single Replacement
• Double Replacement
3 Why do Atoms Form Compounds?
• Stability.
• What makes an atom stable?
• Full outer energy level.
– Eight.
• They can either……
– 1) Gain electrons
– 2) Lose electrons
– 3) Share electrons
4
• A Chemical Bond holds
atoms together in a
compound.
• Two basic types:
1. Ionic
2. Covalent
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Ionic Bonding
Remember: Atoms need a full outer energy level to be stable. EIGHT!
6
Ionic Bonding
OPPOSITS ATTRACT!
7
When Atoms gain or lose electrons,
they are called Ions.
3P
3P
3P
Anion
3P
3P
Cation
3P
• Metals
lose
electrons
to become
stable.
• Nonmetals
gain
electrons
to become
stable.
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9
Atoms can gain or lose electrons
Ionization: requires energy
Why do atoms lose and gain electrons?
To become more stable.
Stability=full outer energy level
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OPPOSITS ATTRACT!
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Properties of Ionic Compounds
• Crystalline solids at room temperature.
• Arranged in repeating threedimensional patterns
• Have high melting points
• Can conduct electricity
when melted or dissolved
in water
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14
Covalent Bonding
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16
Hydrogen and Fluorine
Hydrogen and Chlorine
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Single, Double, Triple
2 e-
4e-
6e-
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Clip
19
Unequal Sharing
Called Polar
δ+
δ_
Polar molecules
happen when
one atom has
a greater
positive charge
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Properties of Covalent Molecules
• Many are gases
or liquids at
room
temperature
• Composed of
two nonmetals.
• Have low
melting and
boiling points
• Ionic and Covalent Bonding Review Clip
21
Covalent or Ionic?
(write the formula, then write “C” or “I”
1. CO2
2. NaCl
3. H2O
4. MgCl2
5. NO2
6. Li2S
7. NaF
clip
9. BeO
10.HCl
11.NaF
12.KCl
13.H2O2
14.N2
15.Cl2
Goals
revisited
22
•Writing chemical formulas is a shorthand way
of indicating what a substance is made of.
•These formulas also let you know how many
atoms of each type are found in a molecule.
The chemical formula for water is H2O.
Carbon Dioxide is CO2.
Why does oxygen combine in different ratios,
in different compounds?
The chemical formula for table salt is NaCl.
Calcium Chloride is CaCl2.
Why does chlorine combine in different
ratios, in different compounds?
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The simplest compounds
are ones with only two
elements
These are called binary
KI, CO, H2O, NaCl
+1
+4
-4
Oxidation numbers
0
Tell you how many electrons an
atom must gain, lose or share to
become stable.
+2
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+3
-3 -2 -1
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Oxidation numbers
+1
-1
Cl
We can predict the ratio
of atoms in ionic
valence
compounds based on 1electron
K
their oxidation numbers
All compounds
are
neutral
Tells you how many
electrons an atom
must gain, lose or
share to become
stable.
KCl
7 valence
electron
+1
-1
Br
Na
NaBr
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+2
Ca
-1
Br
To make it
ZERO, you need
CaBr
1 Ca & 22Br.
Subscripts show the number of atoms of
that kind in the compound
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1.
2.
3.
4.
5.
6.
7.
Now You Try writing Binary
Ionic formulas
K + Br
8. Ga + Br
Mg + Cl
9. Mg + O
Ca + I
10. Al + P
K+O
K+I
Sr + Br
Na + O
Some elements have more than one
oxidation number (Chart p588)
+3
-2
+2
-2
Fe
O
Fe
O
Fe2O3
FeO
We call these elements- Multivalent Elements
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29
Multivalent Practice
1.
2.
3.
4.
Fe+2 + O
Fe+3 + O
Cu+2 + F
Cr+3 + O
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Polyatomic Ions
Cations:
ammonium, NH4+
Anions:
nitrate, NO3-
Groups of
Covalently Bonded
atoms that stay
together.
sulfate, SO42hydroxide, OHphosphate, PO43carbonate, CO32chlorate, ClO3permanganate, MnO4-
chromate, CrO42-
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Try these……p591
1.Na + SO4
2.Mg + PO4
3.Ca + CO3
4.Na + OH
5.Mg + OH
6.NH4 + OH
Mixed Practice
7.K + PO4
8.NH4 + NO3
9.H + SO4
10.Ca + SO4
11.K + NO3
12. Na + PO4
Naming Binary Compounds and
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Molecules
• Steps:
Example:
• NaCl
– If it is Binary1. Decide if it is an ionic or covalent
bond.
– Metal- nonmetal…..
» Ionic
– Nonmetal- nonmetal….
» Covalent
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If ionic …….
2. Check to see if any
elements are
multivalent or
polyatomic.
3. If all single valent,
write the name of
the positive ion
first.
4. Write the root of
the negative ion and
add –ide.
Examples:
1. NaCl
2.K2O
3.AlCl3
4.BaF2
5.KI
6.Li2O
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If ionic …….
Examples:
5. Check to see if any
elements are multivalent. 1.FeO
6. If multivalent ions,
2.Fe2O3
determine the oxidation
3.CuO
number of the element.
7. Use Roman numerals in
4.Cu2O
parentheses after the
5.PbCl4
name of the element.
8. Write the root of the
6.PbI2
negative ion and add –ide.
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If it contains a polyatomic ion...
2. Write the name
Examples:
of the positive
1. NaCO3
ion.
2. KNO3
3. Write the name
of the polyatomic 3. NaC2H3O2
ion.
Example:
•KOH
•Potassium Hydroxide
•CaCO3
•Calcium Carbonate
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If Covalent...
2. Use Greek prefix to
Greek Prefixes
indicate how many atoms
1- monoof each element are in
2- dithe molecule
3- tri3. Add -ide to the more
4- tetraelectronegative element
5pentaExample:
6- hexa•NO
7- hepta•Nitrogen Monoxide
•PCl3
8- octa•Phosphorous trichloride
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Name the following:
Mixed Practice
1. KBr
2. HCl
3. MgO
4. CaCl2
5. H2O
6. NO2
7. CuSO4
8. CaSO4
9. NH4OH
10.CaCO3
11.Cu(ClO3)
12.Cr2O 3
13. FeO
14. LiBr
15 MgCl
2
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Goals
revisited
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Chemical Reactions
• A chemical reaction is a change in which one or more substances are
converted into new substances.
– Rearrangement of bonds in compounds and molecules.
• Chemical Equations make it possible to see clearly what is happening
during a chemical reaction
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Chemical equations are a shorthand way to
show chemical reactions.
Reactants
Products
H2 + O2
H2O
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Conservation of Mass
42
H2 + O2
H2O
Does this meet the Conservation of
Mass
Law?
2 Hydrogen
2 Oxygen atoms
atoms
2 Hydrogen atoms & one Oxygen
atom
Must Balance the Equation to show Conservation
of Mass.
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Can add coefficients to Balance equations.
2 H2 + O2
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Steps:
2 H2O
2
Balanced!!
1. Count Atoms on both sides
2. If not Balanced, add coefficients to balance.
3. Recount atoms after adding each coefficient.
4. Keep adding coefficients until balanced.
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Chemical Reactions
• You start with one or more
compounds and turn it into
different compounds.
Vapors of hydrogen
chloride in a beaker and
ammonia in a test tube
meet to form a cloud of
a new substance,
ammonium chloride.
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1.Synthesis
2.Decomposition
3.Single Replacement (Single
Displacement)
4.Double Replacement
(Double Displacement)
Synthesis
“to make”
A + B
Cu + O
2H + O2
2
AB
CuO
2H O
2
Decomposition
“to breakdown”
AB
A + B
2H O
2
2H + O
NaOH
Na+ OH
2
2
Animation
Single Replacement
When one element replaces another element in a compound
A + BC
Cu+AgNO3
AC + B
Cu(NO3)2+ 2Ag
The more reactive metal will always replace the less reactive metal.
(p749)
Single Replacement
• Clip
Double Replacement
Positive Ion of One compound replaces the positive ion of another
compound and a Precipitate is formed.
AB + CD
AD + CB
Ba(NO3)2+KSO4 2KNO3 + BaSO4
Review Clip
Clip
Animation
Review Clip
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Chemical Reactions and Energy
• All chemical reactions release or absorb energy.
– Heat, light, sound
• Chemical reactions are the making and breaking or bonds.
1. Exergonic
• Chemical reactions that
releases energy are called
exergonic.
– Glow sticks
• If heat is released, it is
called exothermic.
2. Endergonic
• Chemical reactions that require energy are called endergonic.
• Ex: Cold Packs
• If heat is absorbed, it is called endothermic
Catalysts and Inhibitors
Some reactions proceed slowly.
• They can be sped up by a catalysts.
– Catalysts are not used up in the reaction.
– EX: enzymes (biological catalysts)
Some reactions proceed too fast.
• They can be slowed down by inhibitors.
– EX: Preservatives in food
GOALS Revisited…..
1. Compare & contrast ionic and covalent bonds in terms of
electron position.
2. Predict formulas for stable binary ionic compounds based
on balance of charges.
3. Use IUPAC nomenclature for transition between chemical
names and chemical formulas of
• binary ionic compounds
• binary covalent compounds
4. Apply the Law of Conservation of Matter by balancing the
following types of chemical equations:
• Synthesis
• Decomposition
• Single Replacement
• Double Replacement