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Chemistry
Boon
Date: 09/10 & 09/07 2012
NOTES: LEWIS DOT
STRUCTURES PART 2
Catalyst: Mystery Molecules
Write the name of the molecule described:
1. This molecule consists of three atoms. Two
of the atoms are of the same element. The
molecule has two covalent bonds. This
molecule makes up about 60% of a person’s
body weight. It also covers about 70% of the
earth.
2. This molecule consists of 24 atoms. This
molecule is made of atoms of 3 elements. It
is the product of photosynthesis and the
reactant of cellular respiration.
Catalyst Answer 1
 Water! H2O
Catalyst Answer 2
 Glucose C6H12O6
Biology rewind: macromolecules
 All organisms (living things) are made of
macromolecules.
 Macromolecules are covalent compounds.
 The atoms in proteins, carbohydrates, nucleic
acids, and lipids are all connected by covalent
bonds.
Objectives
 I can draw Lewis structures of molecules with
single, double, or triple bonds.
 I know that most biological compounds are
formed by covalent bonds.
 I can state that one mole is 6.02 x 1023
particles.
Agenda
 Catalyst
 HW Review
 Lewis Dot Structures of Molecules Part 2
 Carbon Monoxide Reading Activity
 Covalent Bonds Exit Slip
 Demonstration: Intro to the Mole
 Electron Configuration Practice
HW: Drawing Molecules WS
An electron in the outermost energy level of an
atom that can participate in bonding is called a
valence electron.
2. A structure in which atomic symbols represent
nuclei and inner-shell electrons and in which
dots are used to represent valence electrons is
called a Lewis structure.
3. A possible Lewis structure of a molecule for
which more than one Lewis structure can be
written is called a resonance structure.
1.
HW: Drawing Molecules WS
4. A covalent bond in which two atoms share two
pairs of electrons is called a double bond.
5. A covalent bond in which two atoms share three
pairs of electrons is called a triple bond.
6. A bond in which two atoms share one pair of
electrons is called a single bond.
7. A nonbonding pair of electrons in the valence
shell of an atom is called an unshared pair.
HW: Drawing Molecules WS
8. Methanol CH3OH
9. Propane C3H8
HW: Drawing Molecules WS
10. Water H2O
11. carbon monoxide CO
HW: Drawing Molecules WS
12. Nitryl fluoride NO2F
13. SO32-
HW Vocabulary Crossword
Across
3. Atomic mass
6. Atomic number
9. Ion
10. Period
13. Orbital
16. Nucleus
17. Crystal lattice
18. Octet rule
19. Alkali metal
20. Group
Down
1. Proton
2. Halogen
4. Cation
5. Anion
7. Isotope
8. Electron configuration
11. Noble gas
12. Electronegativity
14. Valence electron
15. Mass number
Chemistry
Date: 09/10 & 09/11 2012
NOTES: LEWIS DOT
STRUCTURES PART 2
Lewis Dot Structures: Part 2
 In a covalent bond, atoms share electrons.
Lewis Dot Structures: Part 2
 A covalent bond in which two atoms share
two pairs of electrons is called a double
bond.
Lewis Dot Structures: Part 2
 A covalent bond in which two atoms share three
pairs of electrons is called a triple bond.
Rules for covalent bonding
 Each bond is made up of 2 electrons
 Each atom wants to reach the same configuration as
the noble gases
 Duet rule: Hydrogen wants 2 valence electrons
 Octet rule: All other atoms want 8 valence electrons
 Atoms will share electrons with other atoms so that
both get a full valence shell
Drawing Lewis Dots for
Compounds
 Steps:
 1. Draw Lewis Dot structures for the
individual atoms
 Double check your numbers of valence e



2. Put central atom in the center
3. Put other atoms around
4. Draw 2 dots between each pair
5. Fill in other dots up to 8 (except for H) –
if the atoms do not have enough valence
electrons to reach 8, a double or triple
bond is necessary.
 6. Replace all bonded pairs with lines
CH4
Central atom
H
H C H
H
Double and Triple Bonds
 What happens when the total electrons do
not match up with the Lewis structure?
 Example:
O2
 Draw the Lewis dot structure:
Total valence electrons:
O
O
O2 = 2 x 6 = 12
Single bonded structure uses too many electrons!
Double Bonds
 If the structure has too many dots, remove
lone pairs from two atoms and replace with a
double bond
Lone pairs
O
O
 In a double bond, the atoms share 4 electrons
 Replace the bonded pairs with 2 lines
Double Bonds
 Some atoms can have more than one double
bond
 Example: CO2
Total valence electrons:
O
C
O
C
= 4
O2 = 2 x 6 = 12
16
Practice
 Carbon dioxide: CO2
 Carbon monoxide: CO
 Sulfur dioxide: SO2
 Nitrogen gas: N2
 Dibromoethene: C2H2Br2
 Ethylene: C2H4
Agenda
 Catalyst
 HW Review
 Lewis Dot Structures of Molecules Part 2
 Carbon Monoxide Reading Activity
 Covalent Bonds Exit Slip
 Demonstration: Intro to the Mole
 Electron Configuration Practice
Carbon Monoxide Reading
 Carbon monoxide is a very dangerous gas.
This article provides vital information about
this deadly gas.
 Instructions: After each paragraph, ask
yourself, “what did I just read?” and “why is
this important?” If you cannot answer these
questions, go back and reread the paragraph.
 After reading, answer the questions at the bottom
of the page.
Agenda
 Catalyst
 HW Review
 Lewis Dot Structures of Molecules Part 2
 Carbon Monoxide Reading Activity
 Covalent Bonds Exit Slip
 Demonstration: Intro to the Mole
 Electron Configuration Practice
Agenda
 Catalyst
 HW Review
 Lewis Dot Structures of Molecules Part 2
 Carbon Monoxide Reading Activity
 Covalent Bonds Exit Slip
 Demonstration: Intro to the Mole
 Electron Configuration Practice
Mole Demonstration…
Substance Name
Observations
Water H2O
Sodium Chloride NaCl
Sucrose C12H24O12
Oleic Acid C18H34O2
Potassium Chloride KCl
•The mole is a number we use to make counting atoms,
ions, and molecules much easier.
•One mole is the number of carbon atoms in 12 grams of
carbon-12.
•One mole is 6.022 x 1023 particles.
Homework
 Due Wednesday 09.12:
 Read textbook pp. 224-229
 Do problems: pp. 233 #1, 2, 4, 5, 6(a), 8(a)
 Due Thursday or Friday 09.13 or 09.14:
 Valence electron and ions review WS