Ionic bonding
(Ch. 7 CP)( Do Block Actitivity)
(Ch. TP)
Focus Question: How and why do elements
combine?
Review:
What are valence electrons? _____________
What is the octet rule? __________
What are cations and anions? ______________
What is electronegativity? _________________
Two types of compound formation at the atomic level:
1. Covalent Bonds - electrons are shared
2. Ionic bonds - electrons are transferred (“stolen”)
Ionic Bonds – occurs between metals (very low
electronegativity) and non-metals (electronegative -high):
@ Nax
+
Cl:

Na+ +
[ Cl ]-
NaCl
Write new electron configuration for both.
@do electron configuration for Na and Cl ions. Then try Mg
and Cl ions  MgCl2.
The strong attractive forces between ions of opposite charges are
called Ionic Bonds. The resulting compounds are called Ionic
Compounds.
When these ions come together, they form crystals.
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A Crystal is regular, repeating arrangement of atoms, ions, or
molecules.
Properties of Crystals:
Strong attractive forces, high melting point, very hard and
brittle, i.e. NaCl – cube shaped, 800°C.
Compounds are represented by formulas. For example:
NaCl – (sodium chloride) table salt
CuO (copper II oxide)
Fe2O3 – rust
H2O – water
Halide anions: Cl-, F-, etc. Group 7A
Chemical Formula (formula unit) - shows the kinds and
numbers of atoms in the smallest representative unit of a
substance.
Example:
Fe2O3 – rust (formula unit – ionic compound)
H2O – water (molecule – Covalent compound)
Structural Formula – shows how the elements are joined.
Ball and Stick:
Space Filling Model:
Electron Dot Structure of K and O:
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K. +
K. + :O  K+ + K+ + O2-
CP: Guided Practice: p.193, 9,10
TP p. 131, 5.3 and 5.4
Charge/Oxidation Number: The charge on the ion when
metals and nonmetals gain or lose electrons. Potassium
has an oxidation number of 1+.
Bonding in metals:
Free floating valence electrons
Ionic Charges:
Group 1A, 2A, and 3A lose electrons – cations. Their
ionic charge is positive and equal to their group number.
Group 5A, 6A, and 7A gain electrons – anions. Their
ionic charge is negative and the number is equal
(Group # - 8 ). For example: Phosphorus
P(5 – 8) = P3Table 7.2 p. 192
The two non-metals in Group 4A usually form
molecular compounds. C and Si.
How do you write the formula for Ionic Cpds.?
Step 1) Write the symbol for the elements or polyatomic
ions. (Cations are always first; anions are last.)
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Step 2) Write the charge (oxidation #) for the elements or
polyatomic ions.
Step 3) Drop the + or – sign, then criss-cross down the
number only.
Step 4) Reduce the subscript if necessary
Step 5) Write the final answer.
Ex:
Sodium Oxide
Na+1 O-2  Na2O
Ex: Use this method to check that the compound is
neutral.
Fe2O3, Iron (III) Oxide (binary ionic cpd) (What is this?)
Find the least common multiple:
Fe = +3 x 2 = +6
O = -2 x 3 = -6
Fe3+ O2-
charge = zero (0)
(p. 153, 26, 27)
Ternary compounds (3 elements):
Calcium Nitrate – Ca2+ and (NO3)Ca2+ (NO3)-  Ca(NO3)2
LiCN – lithium cyanide
Fe(ClO3)3 - Iron(III) Chlorate
NAMING IONIC COMPOUNDS:
Group A metals – name stays the same
Group B metals – name stays the same, but a roman
numeral is added to show the charge (oxidation state).
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Second element’s ending changes to ide.
Transition Metals: may have more than one ion.
Copper(I) and Copper(II) (stock names)
Cu + and
Cu2+
Cuprous ion & Cupric ion (classical)
(Table 5.4, p. 164) Page 255, 9.2
Guided Practice:
Lead, 4 electrons lost  Pb4+ Lead (IV)
Copper, 1 electron lost  Cu+ Copper (I)
Copper (I) chloride, Lead (IV) sulfide
PP: 16, 17, p. 145 cp
PP:p. 140, 5.27  TP
Polyatomic ions: composed of two or more atoms with a
charge.
Sulfite – SO32Sulfate – SO42(Table p. 257, Table 9.3 and Back of PT cp)
Indep. Practice: p. 258, #9 (cp)
Indep. Practice: p. 148, 5.37 (tp)
(Table 5.6, p. 142 tp)
Binary Compounds: compounds composed of two
elements. i.e. KCl (ionic)
Guided and Independent Practice
(p. 207, 45 )cp
(p.140, 5.23) tp
**Cp: p. 282, #67 a thru f
Important Vocabulary
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Hydrates: When water molecules are chemically bonded
to ionic cpds. CuSO4 . 5 H2O (copper(II) sulfate
pentahydrate).
Gypsum (buildings) CaSO4. 2H2O
Applied Chemistry :
Hygroscopic substances - ionic substances that absorb
water from the air. Sodium Carbonate (Na2CO3) and
Sodium Hydroxide (NaOH)
Deliquescent – substances that take enough water from
the air to become liquids by dissolving completely.
What are desiccants and where are they found?
Desiccants are hygroscopic substances that are found in
small packets usually with electronic equipment. (SiO2).
Other places???
Anhydrous Compounds – when a “hydrated” compound
is heated so all the water molecules are driven off.
Example: CuSO4 . 5 H2O becomes CuSO4 (anhydrous)
(TP, Ch 5, p.133) (CP, Ch7, 196-198)
Ionic Properties:
Ionic compounds:
 are composed of well-organized, tightly bond ions.
 are crystalline solids at room temperature.
 are hard, rough and brittle.
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 have high melting points due to the attractions
between the positive and negative charges. (above
300°C)
 dissolve in water and conducts electricity
(electrolytes). Electrolytes are compounds that
conducts electricity when melted or dissolved in
water.
 KCl, CuSO4 , NaCl, NaHCO3
(salt sub., pools, salt, baking soda)
 Representative Unit is a Formula Unit
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