Ionic Bonding
Part I
An Elemental Love Story
Demo
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Burning string demo
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Clean string vs Sugar soaked string vs Salt
soaked string
Any difference?
Research Mission
For this week, you will read articles about:
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Iodine deficiency disorder
Pros and cons of fluoride
The importance of potassium
The dangers of chromium
After gathering information, your group will present
what you learned and how it relates to ions and
ionic bonding.
Before we dive in
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What is a chemical bond?
What are three main different types of
bonds?
Why do elements form ions?
What is a cation?
What is an anion?
Bonds
Q: How do elements combine to form
compounds?
A: Compounds have different forces that hold
groups of atoms together and make them
function as a unit called bonds.
Bonds
Bonds come in three main varieties:
1. Metallic bonds – when metal cations
bond they share a sea of delocalized
electrons.
2. Ionic bonds – transfer of electrons
between metals and non metals
3. Covalent bonds – sharing of electrons
between two nonmetals
Metallic Bonding
Strong forces of attraction are
responsible for the high melting point of
most metals.
Metallic Bonding
 The chemical bonding that
results from the attraction
between metal cations and the
surrounding sea of electrons
 Vacant p and d orbitals in
metal's outer energy levels
overlap, and allow outer
electrons to move freely
throughout the metal
 Valence electrons do not
belong to any one atom
Properties of Metals
 Metals are good
conductors of heat and
electricity
 Metals are malleable
 Metals are ductile
 Metals have high
tensile strength
 Metals have luster
Metal Alloys
 Alloys:
some metal atoms replaced by
others of similar size.
Ionic bonding
Ionic compounds
bond in repeating 3dimensional
patterns with
alternating positive
and negative ions
called crystal
lattice.
Ionic Crystal Lattice Shapes
Ionic bonding
All salts are ionic compounds and form crystals.
NaCl forms the simplest cubic structure
Properties of Ionic Compounds
Structure:
Melting point:
Boiling Point:
Electrical
Conductivity:
Solubility in
water:
Crystalline solids
Generally high
Generally high
Excellent conductors,
molten and aqueous
Generally soluble
Properties of Ionic Compounds
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Lab!
We will be examining the properties of ionic
compounds next double with a lab.
In the meantime, we will move onto how and
why ions bond.
Great BBC video on ions
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http://www.bbc.co.uk/schools/gcsebitesize/sci
ence/add_aqa_pre_2011/atomic/ionicact.sht
ml
Know our ions inside and out
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In order to be successful with ionic bonding,
you need to know what ion each element in
the s and p block will form.
Practice on the Ion worksheet grid in the
packet
The Octet Rule –
Ionic Compounds
Ionic compounds form so that each atom, by
gaining or losing electrons, has an octet of
electrons in its highest occupied energy level.
Ionic bonds form between metals and nonmetals!
• Metals lose electrons to form positivelycharged cations
• Nonmetals gains electrons to form
negatively-charged anions
Ionic Bonding:
Sodium Chloride Example
 Sodium has 1 valence electron
 Chlorine has 7 valence electrons
 An electron transferred gives
each an octet
Na: 1s22s22p63s1
Cl: 1s22s22p63s23p5
Ionic Bonding
Ionic Bonding:
Sodium Chloride Example
This transfer forms ions, each
with an octet:
Na+ 1s22s22p6
Cl-
1s22s22p63s23p6
Ionic Bonding:
Sodium Chloride Example
The resulting ions come together
due to electrostatic attraction
(opposites attract):
Na+ ClThe net charge on the compound
must equal zero
Writing Ionic Compounds with
Electron Dot Diagrams
Drawing Ionic compounds
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How would these elements bond?
Li
F
K
Br
Drawing Ionic Compounds
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Not all relationships are 1:1 with sharing of
valence electrons.
Sometimes you need more of one element
than the other to make a neutral compound
Drawing Ionic Compounds
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How would these elements bond?
Mg
Br
Draw the ionic compounds
How about
K
S
Criss Cross method!
Example: Aluminum sulfide
1. Write the formulas for
cation and anion, including
CHARGES!
2. Do charges balance?
3. If not, use criss-cross
method to balance
subscripts.
3+
Al
2
2S
3
Not balanced!
Now balanced.
= Al2S3
Criss Cross Method!
Example: Beryllium chloride
1. Write the formulas for
cation and anion,
including CHARGES!
2. Do charges balance?
3. Balance charges, if
necessary, using subscripts.
Use criss-cross method to
balance subscripts.
Be2+ Cl-
2
Now balanced.
Not balanced!
= BeCl2
Try the criss cross method
Magnesium chloride: Magnesium
loses two electrons and each
chlorine gains one electron
Mg Cl
Sodium oxide: Each sodium loses
one electron and the oxygen gains
two electrons
Na O
Aluminum sulfide: Each aluminum
loses two electrons (six total) and
each sulfur gains two electrons (six
total)
Al S
Naming Ionic Compounds
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You may have noticed that the name of the
nonmetal in the previous compounds
sounded different (chloride instead of
chlorine, oxygen inside of oxide)
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Can you think of what might be a naming rule for
ionic compounds?
What’s the order we use?
Do any of the names change?
Naming Ionic Compounds
Name the cation first and then the
anion
 Cations – use the name of the
element
 Anions – use the name of the
nonmetal but change the ending to an
–ide
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Metal
Lithium
Sodium
Potassium
Magnesium
Calcium
Barium
Aluminum
Monatomic
Cations
Li+
Na+
K+
Mg2+
Ca2+
Ba2+
Al3+
Ion name
Lithium
Sodium
Potassium
Magnesium
Calcium
Barium
Aluminum
Nonmetal
Ion Name
Fluorine
Monatomic
Anions
F-
Chlorine
Cl-
Chloride
Bromine
Br-
Bromide
Iodine
I-
Iodide
Oxygen
O2-
Oxide
Sulfur
S2-
Sulfide
Nitrogen
N3-
Nitride
Phosphorus
P3-
Phosphide
Fluoride
Practice!
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Let’s try writing our predicting ion charges
and and writing ionic compounds using the
criss cross method
Ionic Bonding Wrinkles
Polyatomic molecules and
METALS WITH MULTIPLE IONS
Polyatomic ions
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Many ionic compounds contain polyatomic
ions which are ions made up of more than
one atom.
Polyatomic ions are atoms that are covalently
bonded together and act as an individual ion.
Because it exists as a unit, DO NOT change
the subscripts within the ion.
In Ionic Compounds, you put ( ) around them
Polyatomic ions
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You will not be asked to memorize the
polyatomic ions, but…
You do need to be able to recognize them
And use a resource to determine its ionic
charge
So that you can balance and write ionic
compounds!
http://www.youtube.com/watch?v=MJZeZvDx
cx8
Polyatomic Ion Names
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CO3 2OH –
SO4 2PO4 3NO3–
ClO3–
NH4 +
carbonate
hydroxide
sulfate
phosphate
nitrate
chlorate
ammonium
Writing Ionic Compound with
polyatomics
Example: Zinc hydroxide
1. Write the formulas for
cation and anion, including
CHARGES!
2+
Zn
2. Do charges balance?
3. Balance charges , if necessary,
using subscripts. Use () if more than
one polyatomic ion. Use criss-cross
method to balance subscripts.
( OH- )2
Now balanced.
Not balanced!
= Zn(OH)2
Example: Barium nitrate
1. Write the formulas for
cation and anion,
including CHARGES!
2. Do charges balance?
2+
(
Ba NO3 ) 2
3. Balance charges , if
necessary, using subscripts.
Use () if more than one
polyatomic ion. Use crisscross method to balance
subscripts.
Now balanced.
Not balanced!
= Ba(NO3)2
Writing Ionic Compound with
polyatomic molecules
Example: Ammonium sulfate (note the 2 word name)
1. Write the formulas for
cation and anion, including
CHARGES!
( NH4+) SO42-
2. Do charges balance?
3. Balance charges , if necessary,
using subscripts. Use () if more than
one polyatomic ion. Use criss-cross
method to balance subscripts.
2
Now balanced.
Not balanced!
= (NH4)2SO4
METALS WITH MULTIPLE IONS
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Up until now, we’ve only been working with
ions from the s and p block and ignoring dblock
This is because d-block metals as well as
other metals can often form more than one
type of ion
Again, you will not have to memorize these
ions, but be able to use a resource to write
ionic compounds with them.
METALS WITH MULTIPLE IONS
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For those metals it is important to represent
which ion it is with a roman numeral.
If it is +1 you put a (I) after the name of the metal
If it is +2 it is a (II) after the name of the metal
If it is a +3, you put a (III) after the name of the
metal
You include this roman numeral in the name
ONLY for metals that form multiple ions!
For example: NiBr2 would be Nickel (II) Bromide
Roman numeral review!
VI
II
III
IV
VII
II
I
III
V
Practice!
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Now, let’s practice writing ionic compounds
with either polyatomic ions or METALS WITH
MULTIPLE IONS