Ionic Compounds and Metals
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Transcript Ionic Compounds and Metals
Chemistry Matter and Change:
Chapter 7
Atoms in ionic compounds
are held together by chemical
bonds formed by the
attraction of oppositely
charged ions.
Ions are formed when
atoms gain or lose valence
electrons to achieve a
stable octet electron
configuration.
•
•
•
Define a chemical bond.
Describe the formation of positive and
negative ions
Relate ion formation to electron
configuration.
Ion
Valence electron
Octet
Electron configuration
Lewis-dot diagrams
Electron affinity
Chemical
bond
Ionic bond
Cation
Anion
The
force that holds two atoms together
Three types
Ionic bonds
Metallic bonds
Covalent bonds
*Chap 7
*Chap 7
*Chap 8
Each valence electron
is represented as a dot
around the nuclear core of the element.
The
most stable electron configuration for
an element is the nearest noble gas.
ns2np6
Octet
Ions gain or
lose electrons to achieve noble
gas configurations
Cation:
a positively charged ion
Results when electrons are lost
Group
1 loses 1 electron
+1 charge
Group
2 loses 2 electrons
+2 charge
Group
13 loses 3 electrons
+3 charge
Groups
3-12 usually lose 2 electrons
Most have +2 charge (range from +1 to +3)
Anion:
negatively charged ion
Formed when electrons are gained
Non-metals
Group
15 gains 3 electrons
3- charge
Group
16 gains 2 electrons
2- charge
Group
17 gains 1 electron
1- charge
A
chemical bond is the force that holds two
atoms together
Some atoms gain or lose electrons to gain a
stable configuration; these are called ions
Most stable configurations end: ns2np6.
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Define a chemical bond.
Describe the formation of positive and
negative ions
Relate ion formation to electron
configuration.
Oppositely charged ions
attract each other forming
electrically neutral ionic
compounds.
Describe
the formation of ionic bonds and
the structure of ionic compounds
Generalize about the strength of ionic
bonds based on the physical properties of
ionic bonds
Categorize ionic bond formation as
exothermic or endothermic
Compound
Chemical
bond
Physical property
Chemical property
Electronegativity
Ionic
bond
Ionic compound
Crystal lattice
Binary compound
Electrolyte
Electrons are exchanged
between atoms
Increases stability of both
Ions are
charges
held together by the opposite
Bond
formed between two elements with an
electronegativity difference > 1.7
Crystallize as sharply defined particles
Formed
from a metal and a non-metal
Contain only two elements
Examoples
NaCl
MgO
CaCl2
Fe2O3
Net charge on all
ions in a compound must
be zero (0)!
More on this later!!!
Crystal
Lattice: Highly organized crystal of
cations and anions
Anion
Cation
Crystalline shape depends on
involved
the ions
Physical
properties
Very strong
Solid at normal temperatures
Very high melting point and boiling point
Many have brilliant colors due to transition metals
Hard, rigid
Brittle
Conductivity
(ability for electric charge to
move through a substance
Solids have electrons locked in place
Non conductive
Aqueous solutions have easily moveable electrons
Electrolytes
Good conductors
Dissolve
in water
May have radically different properties than
the elements that compose them
Polar
Dissolution
Formation of
lattice is always exothermic.
Ionic compounds contain
ionic bonds
formed by the attraction of oppositely
charged ions.
Ions in an ionic compound are arranged in a
repeating pattern called a lattice.
Ionic compounds are electrolytes; they
conduct electricity in liquid and aqueous
states.
Describe
the formation of ionic bonds and
the structure of ionic compounds
Generalize about the strength of ionic
bonds based on the physical properties of
ionic bonds
Categorize ionic bond formation as
exothermic or endothermic
In written names and
formulas for ionic
compounds, the cation
appears first, followed
by the anion.
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Relate a formula unit of an ionic
compound to its composition
Write formulas for ionic
compounds and oxyanions.
Apply naming conventions to ionic
compounds and oxyanions.
Anion
Cation
Metal
Non-metal
Formula unit
Monatomic
ion
Polyatomic ion
Oxidation number
Oxyanion
Formula unit-
simplest way to indicate the
composition of an ionic substance
NaCl
MgCl2
Cl-
Mg2+
Cl-
Ions
in which only one element is present
• Na+, Cl-, Mg2+, P3-
Fancy word
for “charge”
aka oxidation state
Transition metals may have multiple
oxidation states
Must tell the oxidation state
Ex: Iron 2+ is Iron II; Iron 3+ is Iron III
CxAy
C is cation
A is anion
x number of cations in one unit
y is number of anions in one unit
CxAy
Cation is always first
Anion is always second
Net oxidation
MUST BE ZERO
1.
2.
3.
4.
Write out each ion.
Place oxidation number under each ion
Cross multiply
Reduce to simplest form
Sodium
and chlorine
Na
Cl
Sodium
and chlorine
Na
Cl
+1
-1
Sodium
and chlorine
Na
Cl
+1
-1
Na 1 Cl 1
Remove any
NaCl
Reduce
“1”s
if needed
NaCl
Iron
III and oxygen
Fe
O
Iron
III and oxygen
Fe
O
3+
2-
Iron
III and oxygen
Fe
O
3+
2-
Fe2 O 3
Fe2O3
Cannot be reduced
Magnesium
Mg
O
and oxygen
Magnesium
Mg
2+
O
2-
and oxygen
Magnesium
and oxygen
Mg
O
2+
2Mg2 O 2
Mg2O2
Both subscripts can
formula is
MgO
be divided by 2 so the final
Silver
I and chlorine
Magnesium and fluorine
Iron II and oxygen
Calcium and phosphorus
Why did we
specify some
oxidation
numbers, but
not others?
State the name of the cation.
1.
2.
(If using a transition metal, you must state
the oxidation number if there is more than
one possibility.)
State the name of the anion, but change
the ending to “ide.”
NaCl
Sodium chlorine chloride
MgO
Magnesium oxide
K2S
Potassium sulfide
Fe2O3
Iron is a transition metal so we need to figure out
the charge before we can name the compound.
We know oxygen is always -2, so there is an overall
charge of -6 from the oxygen
That means Iron must supply an overall charge of
+6
This indicates that iron must have an oxidation
number of +3 in this case
Fe2O3
Iron III oxide
CuS
AgCl*
H2O
(trick!)
State the name of the cation.
1.
2.
(If using a transition metal, you must state
the oxidation number if there is more than
one possibility.)
Name the anion
AgNO3
Silver nitrate
CaCO3
Calcium carbonate
NH4Cl
Ammonium chloride
FeSO4
Iron II sulfate
1.
2.
3.
4.
Write out each ion.
Place oxidation number under each ion
Cross multiply
Reduce to simplest form
Oxyanions are any
polyatomic anions that
contain oxygen
Your book likes to sound fancy!
You
may not, under any conditions, change
the subscripts within the polyatomic ion
when balancing the charge. You may only
adjust the number of units of each
polyatomic ion!!
Use parentheses to remind yourself that the
units go together and cannot be changed.
Potassium
K
permanganate
(MnO4)
Potassium
K
+1
permanganate
(MnO4)
-1
Potassium
K
+1
permanganate
(MnO4)
-1
K 1(MnO4)1
Potassium permanganate is
K(MnO4)
Calcium
Ca
hydroxide
(OH)
Calcium
Ca
+2
hydroxide
(OH)
-1
Calcium
Ca
+2
hydroxide
(OH)
-1
Ca(OH)2
Ca(OH)2
Ammonium
(NH4)
phosphate
(PO4)
Ammonium
(NH4)
+1
phosphate
(PO4)
-3
Ammonium
(NH4)
+1
phosphate
(PO4)
-3
(NH4)3(PO4)
(NH4)3(PO4)
Hydrogen
peroxide
Sodium nitrite
Calcium sulfate
Aluminum hydroxide
A
formula unit gives the ration of cations to
anions in the ionic compound.
A monatomic ion is formed from one atom.
Roman numerals indicate the oxidation
numbers of any element with more than one
oxidation number.
Polyatomic
ions consist of more than one
atom and act as a single unit.
To indicate more than one polyatomic ion in
a chemical formula, place parentheses
around the polyatomic ion and use a
subscript outside the parentheses.
Relate
a formula unit of an ionic compound
to its composition
Write formulas for ionic compounds and
oxyanions.
Apply naming conventions to ionic
compounds and oxyanions.
Metals
form crystal lattices
and can be modeled as
cations surrounded by a “sea”
of freely moving valence
electrons.
Describe
a metallic bond
Relate the electron sea model the physical
properties of metals
Define alloys and categorize them into two
basic types.
Physical
property
Metal
Malleable
Electron
sea model
Delocalized electron
Metallic bond
Alloy
Lattice structures with
freely moving
electrons
Electrons are not firmly attached to any one
nucleus, but instead “visit” many nuclei
Attraction of
a metallic cation for
delocalized electrons
Freely
moving electrons are referred to as
“delocalized” (lacking a location)
Video
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Melting
and Boiling points
Vary greatly
Most are moderately high melting points and very
high boiling points
Malleability,
ductility and durability
Nuclei move relatively free of each other due to the
sea of electrons
Thermal
and electrical conductivity
Delocalized electrons quickly move heat from one
part of the metal to other parts
Delocalized electrons can move in one direction
and create a “current.”
Hardness
and strength
The number of delocalized electrons plays a role in
the hardness of the metal
More delocalized electrons means a harder metal
Sometimes d level electrons are delocalized as well as the
s resulting in very hard metals.
Alloy-
a mixture of elements that has
metallic properties
Characteristics may differ from the “parent” metals
Include brass, bronze, 14-carat gold, stainless steel,
etc.
Substitutional
Some of the atoms from one metal are replaced by
atoms of the other metal
Ex: brass
Interstitial
Small holes in the lattice are filled by atoms of
another element
Example: Steel
A
metallic bond forms when metal cations
attract freely moving, delocalized valence
electrons.
The electron sea model explains the
physical properties of metallic solids.
Metal alloys are formed when a metal is
mixed with one or more other elements.
Describe
a metallic bond
Relate the electron sea model the physical
properties of metals
Define alloys and categorize them into two
basic types.