Chemical Bonding
Learning Targets
1. Compare and contrast properties of ionic,
covalent, and metallic bonds
2. Draw Lewis Structures
3. Predict and model the geometry of molecules
using VSEPR
4. Describe and identify intermolecular forces of
attraction
5. Write formulas and name compounds
Chemical Bonding
Warm-up 12/15 and 1/6
Observe the substances at the three stations in the
lab area then match each up with the atomic level
visual shown below. Record your answers in your
notebook.
1.)
2.)
3.)
Chemical Bonding
Learning Target #1
Compare and contrast properties of ionic,
covalent, and metallic bonds.
Chemical Bonding
Chemical bond – attraction between atoms,
stabilizes each atom involved
Ionic bonds – chemical bond between a positive
and negative ions due to a transfer of electrons
Covalent bonds – chemical bond between atoms
that have shared electrons
Metallic bonds – chemical bond that results from
the attraction between metal atoms and the
surrounding delocalized electrons
Chemical Bonding
Chemical Bonding
Type of
bond
Name of
compound
formed by
bond
Atoms that
are bonded
Melting
point and
boiling
point
Flexibility
Conducts
electricity?
Covalent
Molecular
Non-metals
Low
High
No
Ionic
Ionic
Metal to
non-metal
High
Low
Yes, when
dissolved
Metallic
N/A
Metals
High
High
Yes
Reflection 12/15 and 1/6
Respond to the prompts in your notebook
1. How did you do with your warm-up
guesses?
2. How does the atomic structure and
bonding of each compound affect their
observable properties?
Warm-up 12/17 and 1/8
1. Why are metals such good conductors of
electricity?
2. How does an IONIC BOND stabilize the
atoms that are bonded together?
3. How does a COVALENT BOND stabilize the
atoms that are bonded together?
Chemical Bonding
Electronegativity: The ability to attract
electrons in a chemical bond.
Chemical Bonding
Reflection – 12/17
1. What are the two ways chemists
use to classify different chemical
bonds?
2. Compare and contrast electron
affinity with electronegativity.
Chemical Bonding
Warm-up 1/7 and 1/11
1. How many valence electrons do
H, B, C, N, O, and F have?
2. How many valence electrons
does a stable atom have?
3. What is the periodic trend for
electronegativity?
Chemical Bonding
Learning Target #2
Draw Lewis dot structures and explain
how they predict the types of bonds
that will stabilize an atom
Chemical Bonding
Lewis structure – Diagram that shows how a molecule is bonded
together; elemental symbols stand for atomic nuclei and innershell electrons, dashes stand for shared pairs bonding pairs of
electrons, and dots stand for unshared or lone pairs of electrons
Chemical Bonding
Lewis Structure Guidelines
1. Arrange atoms as they will be bonded together. Central atom is the least
electronegative and cannot be H.
2. Calculate total # of valence electrons in the molecule.
3. Add an electron for each negative charge, subtract an electron for each
positive charge.
4. Draw single covalent bonds connecting outer atoms with the central
atom. Each bond uses up two electrons.
5. Complete octets starting with outer atoms first using lone pairs of electrons.
6. If you run out of electrons before completing all octets replace lone pairs with
double and triple bonds as needed.
7. If you have extra electrons after completing all octets place additional lone
pairs around the central atom (if in period 3, 4, 5, 6, or 7).
EXCEPTIONS!
1. H can only have 2 valence electrons!
2. B prefers to have only 6 valence electrons!
Chemical Bonding
Activity
As a class we will draw Lewis Structures for
F2, O2, N2, CH2O, and NH4+
Chemical Bonding
Reflection 1/7 and 1/13
1. Draw the Lewis Structure for H2O
2. Label the lone pairs of electrons
3. Label the bonding pairs of electrons
Chemical Bonding
Warm-up 1/8 and 1/13
Draw TWO valid Lewis Structures for ozone.
The formula for ozone is O3.
Chemical Bonding
Warm up 1/12 and 1/27
The hydrogen to oxygen bonds in a water molecule
are “bent” as shown in the model below. Why?
Hint, draw a Lewis Structure for water.
Chemical Bonding
Learning Target #3
Use Valence Shell Electron Pair Repulsion
(VSEPR) principles to predict and model
the geometries and polarity of molecules.
Chemical Bonding
Valence Shell Electron Pair Repulsion
Key principles:
1. Electrons repel each other
2. Electrons are found in bonds and lone
pairs around bonding atoms
3. These electrons will orient as far apart
from each other as possible
4. This determines the 3D shape of a
molecule around a central atom
Chemical Bonding
Valence Shell Electron Pair Repulsion
CO2 has two bonds
The furthest spread is 180⁰ and
results in a LINEAR shape
Chemical Bonding
Valence Shell Electron Pair Repulsion
BH3 has three bonds
The furthest spread is 120⁰ and
results in a TRIGONAL PLANAR shape
Chemical Bonding
Valence Shell Electron Pair Repulsion
CH4 has four bonds
The furthest spread is 109.5⁰ and
results in a TETRAHEDRAL shape
Chemical Bonding
Valence Shell Electron Pair Repulsion
Tetrahedral
Trigonal
pyramidal
Bent
Chemical Bonding
Valence Shell Electron Pair Repulsion
PF5 has five electron domains
The furthest spread is a mix of 120⁰and 90⁰and
results in a TRIGONAL BIPYRAMIDAL shape
Chemical Bonding
Valence Shell Electron Pair Repulsion
SF6 has six electron domains
The furthest spread is a 90⁰and results
in a OCTAHEDRAL shape
Chemical Bonding
Chemical Bonding
Valence Shell Electron Pair Repulsion
This is a great review video for VSEPR
and includes 3D models!
http://ocw.mit.edu/resources/res-tll004-stem-concept-videos-fall2013/videos/representations/vsepr/
Shorter video with just the 3D models
http://www.youtube.com/watch?v=i3F
CHVlSZc4&safe=active
Chemical Bonding
Valence Shell Electron Pair Repulsion
Reflection 1/12
What is the BIG idea behind VSEPR?
Why do scientists care about the
shape of a molecule?
Chemical Bonding
Warm-up 1/26-1/29
What is the molecular
geometry around . . .
Carbon #2
Carbon #9
Nitrogen #8
All of the other Nitrogen
atoms?
Remember to count the
lone pairs and bonds
around each atom!
My good friend, caffeine!
Chemical Bonding
Warm-up 1/28 and 2/1
1.) Rank the following bonds from
least polar to most polar using the
differences in electronegativity.
H-O, H-H, H-F, H-N
2.) The bonds of CO2 are polar but
the molecule itself is not. Using your
knowledge of Lewis Structures and
VSEPR make a guess why that would
be the case.
Chemical Bonding
Learning Target #4
Describe intermolecular forces of attraction
Chemical Bonding
Dipole-dipole forces
The forces of attraction between polar molecules
• Requires a dipole (polar bond)
• Multiple dipoles must be arranged in an additive
manner (not be equal and opposite)
Chemical Bonding
Hydrogen bonding
The forces of attraction between a hydrogen bonded to a
highly electronegative atom and a lone pair of electrons
• Requires a bond or bonds between H-F, H-O, or H-N
• Requires a molecule with lone pairs of electrons
• Strongest IMF
Chemical Bonding
London Dispersion Forces
The forces of attraction caused by temporary dipoles
resulting from the constant movement of electrons
• Present in ALL molecules
• Only IMF present in non-polar molecules
• Weakest IMF
Chemical Bonding
Effects of Intermolecular Forces
• Stronger IMFs hold molecules more closely
together
• Molecules with stronger IMFs have higher
melting points and boiling points
• Molecules with strong IMFs like water display
properties like surface tension and higher
viscosity
Chemical Bonding
Reflection 1/28 and 2/1
• What properties of a molecule are
determined by the strength of its IMFs?
• Rank the following forces of attraction from
weakest to strongest
Hydrogen bonding
Ionic bonding
Dipole-dipole forces
London dispersion forces
Chemical Bonding
Warm-up 2/2 and 2/3
• Pick up and read Lab packet
• Answer “Check for Understanding” questions
• Write down a hypothesis
Chemical Bonding
Warm-up 2/4 and 2/8
What is the charge on a member of hydrogen’s
group (Group 1) when they ionize?
Beryllium’s group (Group 2)?
Fluorine’s group (Group 7)?
Oxygen’s group (Group 6)?
Nitrogen’s group (Group 5)?
Chemical Bonding
Warm-up 2/4 and 2/8
Ionic Bonding Puzzle Lab
•
•
•
•
•
Puzzles and lab sheets up front
Work solo or in pairs
Follow directions carefully
Answer ALL questions
Put pieces back into “envelope” when done
Chemical Bonding
Learning Target #5
Write formulas and name compounds
Chemical Bonding
Chemical formula – recipe for a compound
Chemical Bonding
Writing Ionic Formulas
1. Write the formula for
the two ions, positive
(cation) before
negative (anion)
2. Crisscross charges to
form subscripts
3. Reduce to the lowest
whole # ratio
Chemical Bonding
Naming Ionic Compounds
1. Simply name the two ions in order
from the formula (cation, then anion)
2. Use a Roman numeral if the ion is
variable (determine charge from anion)
Chemical Bonding
Reflection 2/4
1. What does a chemical formula tell you
about a compound?
2. Define polyatomic ion.
3. When is it necessary to use Roman
numerals in the name of an ionic
compound?
Chemical Bonding
Warm-up 2/9 and 2/10
Covalent compounds can combine in
multiple ratios (Dalton’s Law of Multiple
Proportions), how does the naming system
differentiate between these compounds?
Why is this not necessary when naming
ionic compounds?
Chemical Bonding
Writing/Naming Molecular Formulas
1.
2.
3.
4.
Less electronegative atom is first
Prefix indicates how many of each atom
No prefix indicates one atom
Use –ide ending for second atom
CO2
Carbon dioxide
Chemical Bonding
Writing/Naming Molecular Formulas
1.
2.
3.
4.
Less electronegative atom is first
Prefix indicates how many of each atom
No prefix indicates one atom
Use –ide ending for second atom
Chemical Bonding
Reflection 2/9 and 2/10
What makes a naming system successful?
HINT! - Try naming the compounds
below using our system.