Download Unit 5 - Ionic Compounds

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UNIT
Ionic Bonding & Naming
These are your “Yellow Notes”
An Ionic Bond is a chemical bond caused by electrostatic attraction between
cations and anions that is formed by transferring electrons between atoms.
Electrostatic attraction simply means the attraction of opposite charges.
An ionic compound is made up of negative anions bonded to positive cations
resulting in an overall neutral charge.
Ionic Bonds always form between metals and nonmetals.
Metals lose their valence electrons.
Nonmetals gain valence electrons.
Atoms become ions in order to attain a more stable electron arrangement
(an octet of valence electrons).
The octet rule: atoms lose or gain electrons in order to acquire the stable electron
configuration of a noble gas (a stable octet of 8 valence electrons).
Metals lose electrons and become cations (positive ions).
Nonmetals gain electrons and become anions (negative ions).
Metals lose their valence electrons so that they have a full (8) outer
level. Those electrons are transferred to an nonmetal. Nonmetals
gain the number of valence electrons needed to give them a full (8)
outer level.
Since metals lose negatively-charged electrons they become positive
ions. Since nonmetals gain negatively-charged electrons they
become negative ions. The electrostatic attraction between the
positive and negative charges is an ionic bond.
An Ionic Compound is a compound that is held together by ionic bonds.
Table salt (sodium chloride) is a very common ionic compound.
Three physical properties that identify ionic compounds:
They are crystalline solids at room temperature
They have high melting points
They conduct electric current when in a liquid state or in solution (dissolved in water)
Formula Unit: The simplest ratio of ions in an ionic compound
Monatomic Ion: an ion formed by only one type of atom.
Binary Ionic Compound: an ionic compound formed from only two types of
monatomic ions.
The names of Binary Ionic Compounds usually end with the suffix
–ide
The name of the metal is left as is, the nonmetal is changed to end with –ide.
For example:
Sodium bonded with chlorine would be sodium chloride.
Magnesium bonded with oxygen would be magnesium oxide.
Calcium bonded with phosphorus would be calcium phosphide.
Lithium bonded with nitrogen would be lithium nitride.
Strontium bonded with iodine would be strontium iodide.
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Oxidations Numbers / Ionic Charges
1+
2+
3+
3- 2- 1-
Charges Vary For
Transition Metals
ANSWER THESE QUESTIONS (or pay):
What is the charge of all alkali metal ions?
What is the charge of all ions formed from
halogens (halides)?
Nonmetals gain e-
metals lose e-
(high electronegativity)
(low electronegativity)
Determining Chemical Formula Units From Names
Compounds must be neutral!
The positive and negative charges must
add up to zero!
Name:
Sodium Chloride
Symbols:
Na
Cl
Charges:
1+
1-
Formula:
Name:
(adds up to zero)
NaCl
Magnesium Iodide
Symbols:
Mg
I
Charges:
2+
1-
Formula:
Name:
Cross the charges!
(need 2 Iodine to equal zero)
MgI2
Sodium Phosphide
Symbols:
Charges:
What is the charge of the X ion
in the compound X2S ?
Formula:
Name:
Calcium Bromide
Symbols:
Charges:
Formula:
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If the metal in an ionic compound is a TRANSITION METAL,
there is an additional rule for naming the compound!
Most transition metals can have more than one charge (oxidation number).
When naming ionic compounds that have a transition metal we must specify what charge the
transition metal has.
Roman Numerals are used to show the charge of a transition metal ion.
For example, rust is an ionic compound in which the metal (iron, Fe) is a transition metal.
The chemical name for rust is iron(III) oxide
The chemical formula for rust is
nickel(II) bromide
FeO
Fe2O3
The positive and negative charges
still must add up to zero!
Cu2S
iron(II) oxide
Cross the charges!
CuS
nickel(III) bromide
Roman Numerals are used to show the charge of a transition metal ion.
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Polyatomic Ion: An ion made up of two or more atoms bonded together
that acts as a single unit with its own charge.
Common Polyatomic Ions
Name
ammonium
acetate
bicarbonate
hydroxide
nitrate
carbonate
sulfate
phosphate
Ion
NH4+
C2H3O2HCO3OHNO3CO32SO42PO43-
Charge
1+
1111223-
Determining Chemical Formulas for Ionic Compound with Polyatomic Ions
The positive and negative charges
still must add up to zero!
Cross the charges!
Name:
Symbols:
Charges:
Formula:
Potassium Nitrate
K
NO3
1+
1(neutral, adds up to zero)
KNO3
Name:
Symbols:
Charges:
Formula:
Aluminum Sulfate
Al
SO4
3+
2Al2(SO4)3
Name:
Magnesium Hydroxide
When there is only one of a
polyatomic ion, there are
no parentheses!
(2 Al3+ plus 3 SO42- equals zero)
Name:
Symbols:
Symbols:
Charges:
Charges:
Formula:
Formula:
Sodium Nitrate
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Lewis Dot Diagrams for Ionic Compounds
Remember, the metal cation loses electrons and the nonmetal
anion gains electrons in order to become more stable and have
an octet (8 valence electrons).
Valence electrons are TRANSFERRED from the cations to the more
electronegative anions.
The metal cation is shown with an empty outer
level while the nonmetal anion is shown with an
full outer level.
Example:
magnesium fluoride
A magnesium, Mg ion has a charge of 2+
A fluoride, F ion has a charge of 1-
So, the formula must be MgF2
The Lewis Dot Structure for MgF2 would look like this:
Lewis dot diagrams for ionic compounds must show the
oxidation number (charge) of each ion.
Try This:
calcium sulfide
A calcium, Ca ion has a charge of ___
A sulfide, S ion has a charge of ___
So, the formula must be _____________
Draw the Lewis Dot Structure for calcium sulfide in the space below:
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