10/10/23, 2:19 PM Chemistry Final Exam Study Guide
Chemistry 101 Final Exam Study Guide- Spring 2017
Acids and Bases
Acid: substance that provides H+ ions in water
Base: substance that provides OH- ions in water
Covalent Bonds
Review: ionic bonds are formed by the positive charge of the cation being attracted to the
negative charge of the anion
Covalent bonds: bonds formed by sharing electrons between the atoms (not ions)
o 1 electron from each atom (2 atoms per bond)
o Electrons available for bonding are the un-paired electrons in orbitals (orbitals with only
1 electron in them)
Molecule
o A group of atoms held together by covalent bonds
Atoms will bond with enough other atoms to complete the octet
o But they can only form as many bonds as unpaired valence electrons
Hydrogen has 1 valence electron, so it can only form 1 bond, and will not
achieve an octet
Boron has 3 valence electrons, so can only form 3 bonds, and will not achieve
the octet (only 6 electrons)
o There are always exceptions to the rules
Sulfur and phosphorus can extend the octet
Multiple Covalent Bonds between 2 atoms
If the octet is not met, additional bonds may be formed
o Co2 (carbon dioxide)
C has 4 valence electrons, so 4 bonds possible
O has 6 valence electrons, 2 are unpaired, so 2 bonds are possible
PRACTICE
IONS:
Sodium
o Symbol: Na
o Valence: 1
o Electron dot: Na*
o Ionic dot: Na+ (loses its electron to get a 1+ charge)
Magnesium
o Symbol: Mg
o 2 valence E-
o Loses 2 electrons to get 2+ charge
Oxygen
o Symbol: O
o Valence: 6
o Will gain 2 electrons for a 2- charge
Cannot have a covalent bond with ions, just atoms
January 30th, 2017 Lecture
Expanding Condensed Structures
Connectivity is from left to right
Drawing Lewis Structures
1. Determine the total number of valence electrons in the molecule or ion
2. Draw a line between each pair of atoms connected. Each line represents 2 electrons.
3. Use the remaining electrons on the outer atoms to satisfy the octet rule
4. Place any remaining electrons in lone pairs around the central atom
5. If the central atom does not satisfy the octet, use lone electrons from the outer atoms to form
additional bonds between the center and outer atoms.
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,10/10/23, 2:19 PM Chemistry Final Exam Study Guide
Expanding Condensed Structures
Connectivity is from left to right
Drawing Lewis Structures
1. Determine the total number of valence electrons in the molecule or ion
2. Draw a line between each pair of atoms connected. Each line represents 2 electrons.
3. Use the remaining electrons on the outer atoms to satisfy the octet rule
4. Place any remaining electrons in lone pairs around the central atom
5. If the central atom does not satisfy the octet, use lone electrons from the outer atoms to form
additional bonds between the center and outer atoms.
Resonance Structures
If more than one valid Lewis structure can be drawn for a molecule or ion, then the molecule or
ion has resonance, and each of the possible Lewis structures are resonance structures of each
other
Resonance structures are identified by a double-ended arrow pointing between each structure
Number of resonance structures
Look at the number of equivalent atoms surrounding the center atom
o If the bonds between each of the equivalent atoms and the center atom are the same,
there are no resonance structures
o If the bonds between each of the equivalent atoms and the center atom are NOT the
same, there ARE resonance structures
The number of resonance structures is determined by how many spots on the
molecule you can move the different bonds to
February 1st, 2017
Wednesday, February 1, 2017
12:24 PM
VSEPR (Valence Shell Electron Pair Repulsion)
Model used to predict the molecular shapes and geometries of molecules
Identifies the atoms and lone pairs of electrons connected to an atom of interest as an "electron
charge cloud"
AXE designation:
o AXaEb
Where a=number of atoms connected to atom of interest
Where b= number of lone pairs of electrons on the atom of interest
A= center atom
X= other atoms attached to center atom
E= lone pairs of electrons
Geometries of molecules
1. Draw the most stable Lewis structure for the molecule
2. Count the number of electron charge clouds around the atom of interest. An electron charge cloud
can be 1 lone pair of electrons or 1 connected atom
3. The geometry corresponds to the number of electron charge clouds around the atom of interest
a. 2 electron charge clouds= linear
b. 3 electron charge clouds= trigonal planar
c. 4 electron charge clouds= tetrahedral
d. 5 electron charge clouds= trigonal bipyramidal
e. 6 electron charge clouds= octahedral
Shapes of molecules
1. Draw the most stable Lewis structure for the molecule
2. Determine the geometry of the molecule
3. Identify how many electron charge clouds are lone pairs of electrons and how many are atoms
a. If all are atoms, then geometry=shape
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, 10/10/23, 2:19 PM Chemistry Final Exam Study Guide
b. 3 electron charge clouds= trigonal planar
c. 4 electron charge clouds= tetrahedral
d. 5 electron charge clouds= trigonal bipyramidal
e. 6 electron charge clouds= octahedral
Shapes of molecules
1. Draw the most stable Lewis structure for the molecule
2. Determine the geometry of the molecule
3. Identify how many electron charge clouds are lone pairs of electrons and how many are atoms
a. If all are atoms, then geometry=shape
b. If not, move to the next step
2. If lone pairs of electrons exist
Geometry Number of Number of Shape AXE
Atoms Electron Pairs
Linear 2 0 Linear AX2E0
Trigonal 3 0 Trigonal Planar AX3E0
planar
2 1 Bent AX2E1
Tetrahedral 4 0 Tetrahedral AX4E0
3 1 Trigonal AX3E1
pyramidal
2 2 Bent AX2E2
Lecture 12: February 10th
Scientific notation: a compact way to write very large or very small numbers
- Units
o Specific units of measurement are defined by the International System of Units
o Ex. Meters for length/distance, kilograms for mass, kelvin for temperature
Units and Equivalents
Quantity SI Unit (symbol) Metric Unit Equivalents
(symbol)
Mass Kilogram (kg) Gram (g) 1kg=1000g
1kg=2.205lb
Length Meter (m) Meter (m) 1m=3.280ft
Volume Cubic meter (m3) Liter (L) 1 meter
cubed=1000L
1 meter cubed=264.2
gal
Temperature Kelvin (K) Celsius degree © See section 1.11
Time Seconds (s) Seconds (s) -
Metric Prefixes and Scientific Notation
- Metric prefixes
o Used to express very large or very small values
Ex. Easier to express 1,000,000 grams as 1 megagram (Mg)
Ex. Easier to express .000000001 meters as 1 nanometer (nm) or in
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Chemistry 101 Final Exam Study Guide- Spring 2017
Acids and Bases
Acid: substance that provides H+ ions in water
Base: substance that provides OH- ions in water
Covalent Bonds
Review: ionic bonds are formed by the positive charge of the cation being attracted to the
negative charge of the anion
Covalent bonds: bonds formed by sharing electrons between the atoms (not ions)
o 1 electron from each atom (2 atoms per bond)
o Electrons available for bonding are the un-paired electrons in orbitals (orbitals with only
1 electron in them)
Molecule
o A group of atoms held together by covalent bonds
Atoms will bond with enough other atoms to complete the octet
o But they can only form as many bonds as unpaired valence electrons
Hydrogen has 1 valence electron, so it can only form 1 bond, and will not
achieve an octet
Boron has 3 valence electrons, so can only form 3 bonds, and will not achieve
the octet (only 6 electrons)
o There are always exceptions to the rules
Sulfur and phosphorus can extend the octet
Multiple Covalent Bonds between 2 atoms
If the octet is not met, additional bonds may be formed
o Co2 (carbon dioxide)
C has 4 valence electrons, so 4 bonds possible
O has 6 valence electrons, 2 are unpaired, so 2 bonds are possible
PRACTICE
IONS:
Sodium
o Symbol: Na
o Valence: 1
o Electron dot: Na*
o Ionic dot: Na+ (loses its electron to get a 1+ charge)
Magnesium
o Symbol: Mg
o 2 valence E-
o Loses 2 electrons to get 2+ charge
Oxygen
o Symbol: O
o Valence: 6
o Will gain 2 electrons for a 2- charge
Cannot have a covalent bond with ions, just atoms
January 30th, 2017 Lecture
Expanding Condensed Structures
Connectivity is from left to right
Drawing Lewis Structures
1. Determine the total number of valence electrons in the molecule or ion
2. Draw a line between each pair of atoms connected. Each line represents 2 electrons.
3. Use the remaining electrons on the outer atoms to satisfy the octet rule
4. Place any remaining electrons in lone pairs around the central atom
5. If the central atom does not satisfy the octet, use lone electrons from the outer atoms to form
additional bonds between the center and outer atoms.
about:blank 1/18
,10/10/23, 2:19 PM Chemistry Final Exam Study Guide
Expanding Condensed Structures
Connectivity is from left to right
Drawing Lewis Structures
1. Determine the total number of valence electrons in the molecule or ion
2. Draw a line between each pair of atoms connected. Each line represents 2 electrons.
3. Use the remaining electrons on the outer atoms to satisfy the octet rule
4. Place any remaining electrons in lone pairs around the central atom
5. If the central atom does not satisfy the octet, use lone electrons from the outer atoms to form
additional bonds between the center and outer atoms.
Resonance Structures
If more than one valid Lewis structure can be drawn for a molecule or ion, then the molecule or
ion has resonance, and each of the possible Lewis structures are resonance structures of each
other
Resonance structures are identified by a double-ended arrow pointing between each structure
Number of resonance structures
Look at the number of equivalent atoms surrounding the center atom
o If the bonds between each of the equivalent atoms and the center atom are the same,
there are no resonance structures
o If the bonds between each of the equivalent atoms and the center atom are NOT the
same, there ARE resonance structures
The number of resonance structures is determined by how many spots on the
molecule you can move the different bonds to
February 1st, 2017
Wednesday, February 1, 2017
12:24 PM
VSEPR (Valence Shell Electron Pair Repulsion)
Model used to predict the molecular shapes and geometries of molecules
Identifies the atoms and lone pairs of electrons connected to an atom of interest as an "electron
charge cloud"
AXE designation:
o AXaEb
Where a=number of atoms connected to atom of interest
Where b= number of lone pairs of electrons on the atom of interest
A= center atom
X= other atoms attached to center atom
E= lone pairs of electrons
Geometries of molecules
1. Draw the most stable Lewis structure for the molecule
2. Count the number of electron charge clouds around the atom of interest. An electron charge cloud
can be 1 lone pair of electrons or 1 connected atom
3. The geometry corresponds to the number of electron charge clouds around the atom of interest
a. 2 electron charge clouds= linear
b. 3 electron charge clouds= trigonal planar
c. 4 electron charge clouds= tetrahedral
d. 5 electron charge clouds= trigonal bipyramidal
e. 6 electron charge clouds= octahedral
Shapes of molecules
1. Draw the most stable Lewis structure for the molecule
2. Determine the geometry of the molecule
3. Identify how many electron charge clouds are lone pairs of electrons and how many are atoms
a. If all are atoms, then geometry=shape
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, 10/10/23, 2:19 PM Chemistry Final Exam Study Guide
b. 3 electron charge clouds= trigonal planar
c. 4 electron charge clouds= tetrahedral
d. 5 electron charge clouds= trigonal bipyramidal
e. 6 electron charge clouds= octahedral
Shapes of molecules
1. Draw the most stable Lewis structure for the molecule
2. Determine the geometry of the molecule
3. Identify how many electron charge clouds are lone pairs of electrons and how many are atoms
a. If all are atoms, then geometry=shape
b. If not, move to the next step
2. If lone pairs of electrons exist
Geometry Number of Number of Shape AXE
Atoms Electron Pairs
Linear 2 0 Linear AX2E0
Trigonal 3 0 Trigonal Planar AX3E0
planar
2 1 Bent AX2E1
Tetrahedral 4 0 Tetrahedral AX4E0
3 1 Trigonal AX3E1
pyramidal
2 2 Bent AX2E2
Lecture 12: February 10th
Scientific notation: a compact way to write very large or very small numbers
- Units
o Specific units of measurement are defined by the International System of Units
o Ex. Meters for length/distance, kilograms for mass, kelvin for temperature
Units and Equivalents
Quantity SI Unit (symbol) Metric Unit Equivalents
(symbol)
Mass Kilogram (kg) Gram (g) 1kg=1000g
1kg=2.205lb
Length Meter (m) Meter (m) 1m=3.280ft
Volume Cubic meter (m3) Liter (L) 1 meter
cubed=1000L
1 meter cubed=264.2
gal
Temperature Kelvin (K) Celsius degree © See section 1.11
Time Seconds (s) Seconds (s) -
Metric Prefixes and Scientific Notation
- Metric prefixes
o Used to express very large or very small values
Ex. Easier to express 1,000,000 grams as 1 megagram (Mg)
Ex. Easier to express .000000001 meters as 1 nanometer (nm) or in
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