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A compound is a pure substance composed of
more than one atom
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A chemical bond is a mutual electrical
attraction between atoms in a compound
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Compounds can either be molecular or ionic
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There are two types of bonding:
1. Ionic Bonds result from the transfer of electron from
metal to nonmetal
2. Covalent Bonds result from the sharing of electrons
between two atoms
▪
▪
Polar covalent = unequal sharing
Non-polar covalent = equal sharing
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Composed of oppositely charged ions
Composed of Metal + nonmetal
 Metals form cations (+)
▪ Low IE and low EA mean these atoms lose electrons readily
 Nonmetals form anions (-)
▪ high IE and high EA mean these atoms gain electrons readily
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Electrically neutral
Formula unit: lowest whole # ratio of ions in
the compound
EX: NaCl, CaF2
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Solids at room temperature
High melting point (>4000C)
Soluble in water
Conduct electricity when melted or dissolved in
water
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Composed of two or more nonmetals
Involve covalent bonding (Electrons are shared)
 Sharing “tricks” each element into thinking that their
outer shells are filled
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Molecule: smallest unit of a molecular compound
Molecular formula: tells the type and number of
atoms in a molecule
 Ex: H2O, CO2, CO
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low melting point (<4000C)
Usually NOT soluble in water
DO NOT conduct electricity
Metal + nonmetal = ionic
Nonmetal + nonmetal = molecular
NaCl
CO
LiF
H2O
MgS
More
practice
in packet
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DUE MONDAY!!!
Ion Flashcards…
 Name of ion on one side
 Symbol with charge on the other side
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6 sets…keep them separate
 Quizzes will begin next week…one set at a time
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Chemical formulas show the kinds and numbers of
atoms in the smallest representative unit of that
compound
 For example, CO2, the formula for carbon dioxide tells
us that one carbon atom and two oxygen atoms form
one molecule of CO2
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Chemical formula for a covalent compound
Show kind and number of atoms in a molecule
Does not give any information about structure

A variety of diagrams and molecular models
can be used to show molecular structure
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Noble gases stand alone, do not combine
chemically with any other element
7 elements exist as diatomic molecules
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Hydrogen = H2
Oxygen = O2
Nitrogen = N2
Fluorine = F2
Chlorine = Cl2
Bromine = Br2
Iodine = I2
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A formula unit tells the whole-number ratio of
ions in an ionic compound
 Ionic compounds do not exist as single units
 NaCl = 1:1 ratio
 MgCl2 = 1:2 ratio
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Atoms combine in whole number ratios so
that the masses of elements in a compound
are also in the same proportion
Apply the rule for naming and writing formulas for molecular compounds
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A molecular compound composed of only two
non-metallic elements
 For example: H2O,
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Atoms can often bond in more than one way
 For example, CO vs CO2

Naming conventions are important
 Carbon monoxide will kill you, carbon dioxide will not

Used to describe number of atoms of each
element present in one molecule

Carbon monoxide
 Prefix mono = one
 CO

Carbon dioxide
 Prefix di = two
 CO2
Notice…NO mono prefix on the first element

Identify the prefix and the element that the prefix
is attached to
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Write the correct symbols for each element with
the appropriate subscripts

Example: tetraiodine nonoxide
 Tetra = 4 so there are 4 iodine atoms
 Non or nona = 9 so there are nine oxygens
 Molecular formula = I4O9
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Sulfur trioxide
Phosphorous pentafluoride
Dinitrogen monoxide
Phosphorous trichloride
Dichlorine octaoxide
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Subscript after the symbol for the element will tell
the prefix to use for that element
 For example, CO2 the #2 tells you there are two oxygen
atoms therefore, oxygen will get the prefix
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If first element in formula is only one, no prefix
 For example, wouldn’t say monocarbon dioxide, just
carbon dioxide
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End molecular names with -ide
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CS2
N 2O 3
OBr2
SO3
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Carbon disulfide
Dinitrogen trioxide
Oxygen dibromide
Sulfur trioxide
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Electrons in the highest occupied energy level
Involved in bonding
Determine the chemical properties of the
element
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Look at electron configuration or group # on
periodic table
For example, Na
 Electron configuration = 1s22s22p63s1 1 valence e All elements in group 1A have 1 valence e-
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For example, Cl
 Electron configuration = 1s22s22p63s23p5 7 valence e All elements in group 7A have 7 valence e-
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Also called Lewis Dot diagrams
Show valence electrons around element symbol
Do not distinguish between s and p orbitals
Example: chlorine (7 valence electrons)
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all atoms want to achieve “NOBLE” status and be
just like the NOBLE gases
 Noble gases have 8 valence electrons (octet)
▪ Except helium which has only 2

Atoms will interact in a way to fill their outer
energy level so that it contains 8 electrons
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Electron dot diagrams can be used to show
bonding

Oxygen (group VIA; atomic#8)
 How many valence electrons?
 How many more valence electrons needed to be
stable?
 How many bonds will oxygen form?
Covalent Bonds
Rewritten as
Covalent Bonds
Rewritten as
Identify the elements that the color spheres in
your kit will represent
1.

If you have a blue sphere with 5 holes, connect two of
the holes with a spring
Build the 3-D model, draw it to the best of your
ability
Structural formula = Lewis dot diagram without
unshared electrons represented
2.
3.

Do not try to recreate you ball and stick model
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Electronegativity = tendency of an atom to
attract electrons
Differences in electronegativities determine the nature
of the bond

If less than 0.4 = nonpolar covalent
 equal sharing of electrons between atoms
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If between 0.4 and 1.67 = polar covalent
 unequal sharing of electrons

If greater than 1.67, IONIC
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1.
2.
3.
Polar covalent?
Nonpolar covalent?
Ionic?
Na and Cl (0.9 vs 3.0)
carbon and hydrogen (2.5 vs 2.1)
hydrogen and oxygen (2.1 vs 3.5)
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1.
2.
3.
Polar covalent?
Nonpolar covalent?
Ionic?
Na and Cl (0.9 vs 3.0)
carbon and hydrogen (2.5 vs 2.1)
hydrogen and oxygen (2.1 vs 3.5)
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Stands for Valence Shell Electron Pair Repulsion
Predicts the shapes of molecules
Depends on the # of electrons or atoms bonded to
a central atom
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Bonding groups: 2
Nonbonding pairs: 0
 Examples:
▪ BeCl2
▪ CO2
▪ HCN
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# of atoms or electron pairs: 2
# of unshared pairs: 1 or 2
 Examples:
▪ H2O
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Bonding pairs: 3
Nonbonding pairs: 0
 Examples:
▪ BF3
▪ COCl2
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Bonding pairs: 3
Nonbonding pairs: 1
 Examples:
▪ NH3
▪ NF3
▪ PCl3
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Bonding pairs: 4
Nonbonding pairs: 0
 Examples:
▪ CH4
▪ CCl4