Ionic Bonding
Science 10
1
Keeping Track of Electrons
• The electrons responsible for the chemical
properties of atoms are those in the outer
energy level.
• Valence electrons – The electrons in the outer
energy level (in valence shell).
• Kernel (core) electrons -those in the energy
levels below the valence shell.
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Keeping Track of Electrons
• Atoms in the same column
• Have the same number of outer electrons
(valence electrons).
• Easily found by looking up the group number on
the periodic table.
• Group 2 - Be, Mg, Ca, .- 2 valence electrons
• The last digit in the representative group
number gives the number of valence electrons
3
Electron Dot diagrams (Lewis Structure)
• A way of keeping track of
valence electrons.
• How to write them
• Write the symbol.
• Put one dot for each valence
electron
• Don’t pair up until they have
to
X
4
The Electron Dot diagram for
Nitrogen
Nitrogen has 5 valence
electrons.
 First we write the symbol.
Then add 1 electron at a
time to each side.
Until they are forced to pair up.

N
5
Write the electron dot diagram for
•
•
•
•
•
•
•
Na
Mg
C
O
F
Ne
He
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Electron Configurations for Cations
• Metals lose electrons to attain noble gas
configuration (Born losers).
• They make cations (positive ions).
• If we look at electron configuration it
makes sense.
• Na 2, 8, 1 - 1 valence electron
• Na+ 2, 8 -noble gas configuration (Ne)
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Electron Dots For Cations
• Metals will have very few valence electrons
Ca
Calcium has two valence electrons (Group 2)
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Electron Dots For Cations
• Metals will have very few valence electrons
• These will come off
Ca
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Electron Dots For Cations
• Metals will have very few valence electrons
• These will come off
• Forming cations (positive ions)
2+
Ca
Calcium has lost two valence electrons
10
Electron Configurations for Anions
• Nonmetals gain electrons to attain noble gas
configuration.
• They make anions (negative ions).
• If we look at electron configuration it makes
sense.
• S 2, 8, 6 - 6 valence electrons
• S2- 2, 8, 8 -noble gas configuration (Ar).
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Electron Dots For Anions
• Nonmetals will have many valence electrons.
• They will gain electrons to fill outer shell.
P
3P
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Stable Electron Configurations
• All atoms react to achieve noble gas
configuration.
• Noble gases have 8 valence electrons .
• Also called the octet rule.
Ar
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Ionic Bonding - the basics
• Metals form positive ions.
• Non-metals form negative ions.
• Anions and cations are held together by opposite
charges.
• Ionic compounds are called salts.
• The bond is formed through the transfer of electrons.
(From metals to nonmetals.)
• Electrons are transferred to achieve noble gas
configuration.
• The valence electrons determine the formula. (Simplest
ratio is called the formula unit.)
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Ionic Bonding
Na
Cl
15
Ionic Bonding
+
Na
-
Cl
Na lost 1 electron to form 1+ cation
Cl gains 1 electron to form a 1- anion
The + and – attract (force of attraction is called an
ionic bond) holds the ions together.
The ratio is 1:1 so the formula is NaCl
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Counting Electrons
During the formation of an ionic compound the total
number of electrons lost (by metals in forming
cations) must equal the total number of electrons
gained (by non-metals in forming anions).
Ca Group 2 loses 2 eP Group 15 (5A) gains 3eTo keep totals equal a LCM of 6 is used.
Therefore: 3 x Ca = 3 x 2+ = 6+
2 x P = 2 x 3 - = 66 lost (+6) = 6 gained (6-) Charges cancel.
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Ionic Bonding
• All the electrons must be accounted for,
total lost = total gained!
Ca
P
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Ionic Bonding
Ca
P
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Ionic Bonding
2+
Ca
P
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Ionic Bonding
2+
Ca
P
Ca
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Ionic Bonding
2+
Ca
3-
P
Ca
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Ionic Bonding
3-
2+
Ca
P
Ca
P
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Ionic Bonding
3-
2+
Ca
P
2+
Ca
P
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Ionic Bonding
Ca
2+
Ca
P
2+
Ca
P
3-
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Ionic Bonding
Ca
2+
Ca
3P
2+
Ca
P
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Ionic Bonding
2+
Ca
2+
Ca
2+
Ca
3-
P
3-
P
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Ionic Bonding
The Ca to P ratio is 3:2 so:
Formula Unit
Ca3P2
3 x 2+ = 6+
2x3–=6–
6+ +
6– = 0
(# e– lost = # e– gained)
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+1
+2
+3
+4
-3
-2
-1
Most Transition Metals do not have form
cations of one fixed charge, they tend to
have variable charges.
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0
Properties of Ionic compounds:
• High melting points.
• Conduct electricity when dissolved in water or in
molten state.
• They do not conduct electricity in solid state because
the electrons are not able to move.
• Ionic substances tend to be electrolytes - a substance
that dissolves in water to produce a solution that will
conduct electricity.
• Solid are a crystal lattice.
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Some common binary ionic
compounds:
•
•
•
•
NaCl – table salt
KCl – potash
AlCl3 antiperspirant
CaCl2 – road salt
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Naming fixed binary ionic compounds
• Ionic compounds are formed between metals and
non-metals. When naming them, we name the
Cation (metal) first, then we name the anion (nonmetal) last- changing the last part of the name of the
element to “ide”.
• Ex: chlorine – chloride
•
oxygen – oxide
•
nitrogen - nitride
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Formula Writing and Naming:
Fixed Binary ionic compounds
• Formula: write the cation first and anion last.
• Name: Name the cation first (use the element name)
• Name the anion but change the ending to “ide”
So, Formula: KCl
Name: potassium chloride
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Example- Show the formation of the
compound formed between Na and O.
Formula Na2O
Name: sodium oxide
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Show the formation of CaCl2.
Name: calcium chloride
35
• Show the formation of the following fixed binary ionic
compounds using electron-dot structures (Lewis
structures). Also write the names of the compounds.
• a) K3P
• b) NaF
• c) Al2O3
• Predict the formula and name the compounds formed
when the following elements react.
• a) K and F
• b) Li and O
• c) Mg and P
36
Write the formula and the name for the ionic
compound formed from each of the following
ions.
• a) Ca2+ and Cl• b) Al3+ and N3• c) Be2+ and O2• d) Be2+ and N3• e) K + and S2-
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Practice: Name the following binary
ionic compounds:
A) MgO
B) Al2S
C) K3N
D) ZnF2
E) CaCl2
F) LiCl
G) CsF
H) NaBr
I) BaF2
J) HCl
Magnesium oxide
Aluminum sulfide
Potassium nitride
zinc fluoride
calcium chloride
Lithium chloride
Cesium fluoride
Sodium bromide
Barium bromide
Hydrogen chloride
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What about those ones in the
“middle”?
• Metals, so they form positive ions (cations)
• They can form different ions (variable charge)
eg, Fe2+, Fe3+
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Examples….
40
Naming variable binary ionic
compounds
• Ionic compounds formed between metals with
variable charge and non-metals. When naming
them, we name the metal first and state the charge
in Roman numerals in brackets , then we name the
non-metal last- changing the last part of the name of
the element to “ide”.
• Roman numerals:
• 1–I
4 – IV
7 – VII
10 – X
• 2 – II
5–V
8 – VIII
• 3 – III
6 – VI
9 – IX
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Ionic compounds with transition metals:
FeCl3
Fe3+
Cl
Fe
3Cl1-
Cl
FeCl3
Cl
iron(III) chloride
Cu2S
Cu
S
Cu
2Cu1+
S2-
copper(I) sulfide
42
Write the formulas for the following compounds.
a) copper(I) oxide
b) lead(IV) bromide
c) iron(III) sulfide
d) nickel(III) fluoride
e) manganese(IV) sulfide
Write the names of the following compounds.(Use the
anion to calculate the charge of the cation.)
a) FeCl2
b) FeO
c) Cu2O
d) PbO2
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Polyatomic ions…ions made up of 2 or more
elements.
44
Ionic compounds with polyatomic ions…
NH41+
and
S2-
NH4 1+
S
2NH41+
S2-
2-
NH4 1+ Charges cancel
(NH4)2S
ammonium sulfide
45
Write the formula for the following ionic compounds
a) Ca2+ & NO31b) Na1+ & OH1c) K1+ & SO42d) Ba2+ & PO43e) Li1+ & HCO31-
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Naming Ionic Compounds with polyatomic ions
Name the cation: 1) fixed name the element
2) variable element name
followed by (roman numeral)
3) name the positive polyatomic
(only for NH41+) then the anion
Name the negative polyatomic ion
Write the name for the ionic compounds from the
previous slide.
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