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1.3 Bonding
INTRAMOLECULAR BONDS
ALWAYS REMEMBER THAT THIS TYPE OF BOND IS VERY STRONG
An intramolecular bond always exists within a compound.
There are 4 types of intramolecular bonds:
1) Ionic
2) Covalent
3) Dative Covalent Bonds (Also called a coordinate bond)
4) Metallic Bonds
IONIC BONDING
Definition: An Ionic bond is the electrostatic force of attraction between oppositely charged
ions formed by electron transfer.
Metal atoms lose electrons to form positive ions. Non-metal atoms gain electrons to form
negative ions
REMEMBER:
lose electrons to form positive ions
 When non-metals react to form compounds they gain electrons to form negative

When metals react to form a compound they
ions
QUESTION: Give the dot and cross diagrams to show ionic bonding in the following compounds:
1. Sodium bromide
2. Calcium oxide
3. Magnesium chloride
4. Lithium oxide
5. Aluminium oxide
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Strength Of Ionic Bonds & Charge Density
The strength of an ionic bond depends on how strong the attractive forces are between the
oppositely charged ions
The strength of these attractive forces is dependent on two factors:
i.
The size of the ionic radius
ii.
The charge on the ion
+
2In general, if the size of the ionic radius is small (i.e. Li or O ) OR the charge on the ion is high
3+
(i.e. Al OR N3-) than these ions will have a high charge density and so attract he oppositely
charged ion more strongly. Hence these compounds will have higher melting points
Question: Which compound has the higher melting point and why?
MgO OR NaCl
ANSWER:
MgO has the higher melting point since Mg2+ has a higher charge and is a smaller ion
compared to Na+ ∴ has a higher charge density compared to Na+, whereas O2- has a higher
charge compared to Cl- ∴ has a higher charge density, So the electrostatic force of attraction
between Mg2+ and O2- is stronger than Na+ and Cl-, so more energy is needed to overcome the
bond.
COVALENT BONDING
Definition: A covalent bond is a shared pair of electrons between the nuclei of two atoms
QUESTION – Give the dot and cross diagrams to show covalent bonding in:
1. H2
2. HCl
3. Cl2
4. CH4
5. NH3
6. H2O
7. O=O
8. O=C=O
9. C2H6
10.
C2H4
11.
N≡N
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1.
4.
7.
10.
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2.
3.
5.
6.
9.
8.
11.
BONDING NOTES MISS CHOHAN
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Dative Covalent bonding
DEFINITION: A Dative covalent bond
forms when the shared pair of
electrons in the covalent bond come
from only one of the bonding atoms or
an ion. A dative covalent bond is also
called co-ordinate bonding
Common examples you should be able
to draw that contain dative covalent
bond (e.g. NH4+, H3O+, NH3BF3 )
The dative covalent bond
acts like an ordinary
covalent bond when
thinking about shape so
The direction of the
arrow goes from the
atom that is providing
the lone pair to the atom
that is deficient
in NH4+ the shape is
tetrahedral
METALLIC BONDING
Definition: A metallic bond is the electrostatic force of attraction between the positive
metal ions and the delocalised electrons
Positive metal cations
Delocalised free moving
electrons
BONDING NOTES MISS CHOHAN
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The three main factors that affect the strength of a metallic bond are:
1. Number of protons/ Strength of nuclear attraction. The more protons the stronger the
bond
2. Number of delocalised electrons per atom (the outer shell electrons are delocalised) The
more delocalised electrons the stronger the bond
3. Size of ion. The smaller the ion, the stronger the bond.
Example
Mg has stronger metallic bonding than Na and hence a higher melting point. The Metallic
bonding gets stronger because in Mg there are more electrons in the outer shell that are
released to the sea of electrons. The Mg ion is also smaller and has one more proton. There is
therefore a stronger electrostatic attraction between the positive metal ions and the
delocalised electrons and higher energy is needed to break bonds.
TREND IN STRENGTH OF METALLIC BOND ACROSS A PERIOD
1+
2+
3+
As you go along a period the strength
of a metallic bond increases.
QUESTION:
BONDING NOTES MISS CHOHAN
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BONDING NOTES MISS CHOHAN
12/13/2015