Chemical Bonds Chapter 22

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Chapter 22
Chemical Bonds
22.1 Stability in Bonding
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Most elements are found combined with
other elements because they are not
chemically stable (compounds)
Noble gases are mono-atomic (6% elements)
Chemical stability depends on valence
electrons
Compounds have different properties than
the elements that compose it
Ex. Na, Cl, NaCl from chapter 18
Writing Chemical Formulas
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Chemical Formula: represents a chemical
compound
Uses symbols for the elements
The subscript numbers show the ratio of ions
in the compound
Formulas are like cooking recipes
Write the Formula For:
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Sodium chloride
Magnesium oxide
Aluminum oxide
Iron (III) oxide
Calcium fluoride
Strontium phosphate
Barium nitrate
Write the Name for:
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K2O
Al2O3
Mg3N2
CaCO3
NaNO3
Calculate the molecular weight for each of
the above:
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Stable Electron Configurations
– When outermost energy level is full - Atom is
stable (pg. 690)
– Not likely to react with other elements
– Electron dot diagram – model of atom with
symbol of element in the center and the
valence electrons represented by dots
around the symbol
– Pg. 690, 691
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Chemical bonding occurs when elements
bond with other elements or themselves to
achieve stability in their valence levels
Atmospheric gases exist as molecules
–
–
–
–
Hydrogen
Oxygen O2
Nitrogen
Chlorine
H2
N2
Cl2
Ionic Bonds
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Metals combine with Nonmetals
Transfer of electrons to become more stable
Ions – when an atom gains or loses
electrons “charged atom”
Electrons no longer equal the protons – the
atom becomes charged
Draw NaCl, MgO, Al2O3
Anions and Cations
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Loses electrons – makes positive ion or
– Ex. Na+ sodium ion
“metals”
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Gains electrons – makes negative ion or anion –
add suffix -ide Ex. Cl- chloride ion
“nonmetals”
Ionic bond – force that holds anions and cations
together
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cation
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Ionic bond: formed when electrons are
transferred from one atom to another
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Ionization Energy: – energy required to
remove an electron
Ionic Compounds: – Compounds that
contain ionic bonds
Chemical Formula: – shows the elements
and ratio of atoms in a compound
Crystal Lattices: – arrangement of ions in
a repeating pattern – forms solid crystals
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6.2 Covalent Bonding
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Nonmetals combine with nonmetals
Sharing electrons to become stable
Covalent Bond – when two atoms share one
pair of valence electrons – single bond
Two pairs – double bond
Three pairs – triple bond
Polar Covalent Bonds
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Electrons are not shared equally
Atom with greater attraction for electrons
has a partial negative charge
Other atom has a partial positive charge
Ex. Water – H2O
Ex. Carbon Dioxide – CO2
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Polyatomic Ions – a group of covalently
bonded atoms with a positive or negative
charge and acts as a unit
Prefix poly- means “many”
Most polyatomic ions are anions
Page 707
6.3 Naming Compounds
and
Writing Formulas
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Chemical Formula: represents a chemical
compound
Uses symbols for the elements
The subscript numbers show the ratio of
ions in the compound
Ionic Compounds
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Write symbol of cation (metal) first
followed by the symbol of the anion
(nonmetal) Ex. NaCl
Use subscripts to show the ratio
Criss cross the oxidation numbers
Add the suffix “ide” to the nonmetal when
naming these
Covalent compounds
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Name and formula describe the type and
number of atoms in each molecule
Prefixes on page 709
Use prefixes to tell how many atoms of
each element
Ex. N2O4
dinitrogen tetraoxide
6.4 The Structure of Metals
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Metallic Bond – the attraction between a
metal cation and the shared electrons that
surround it
The more valence electrons in the shared
pool, the stronger the metallic bond
Alloys
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A mixture of 2 or more elements, one of
which is a metal – has properties of both
metals
Copper Alloys – copper + tin = bronze
copper + zinc = brass
Steel Alloys – iron + carbon = steel
iron + chromium = stainless steel
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