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8/10/2019 Chemistry chapter 5 form 4
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CHAPTER 5 :
CHEMICAL BONDS
1
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IONIC BONDING
Ionic compound - Chemical compound formed by
transfer of valence electrons from metal
atom to non-metal atom.
Ionic bond - A strong bond formed when
positive ions and negative ions are attractedby the electrostatic forces.
CHEMICAL BONDS
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THE FORMATION OF IONS
When an atom releases or accepts electrons, it
becomes a charged particle called an ion.
An atom that accepts electrons forms a negative ioncalled anion.
An atom that donates electrons forms a positive ioncalled cation.
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Mg
2.8.2 2.8
Magnesium atom Magnesium ion
donates 2 electrons
Mg
2+
ELECTRON ARRANGEMENTS
FOR THE IONS FORMED
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ELECTRON ARRANGEMENTS
FOR THE IONS FORMED
2.8.72.8.8
ClCl
-
Chlorine atom Chloride ion
accepts 1 electron
+
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Formation of Ionic Bond
The formation of sodium chloride (NaCl)Sodium atom releases one electron to achieve the stable octetelectron arrangements.
Chlorine atom accepts one electron from the sodium atom to
achieve stable octet electron arrangement.The ions are held together by a strong electrostatic force betweenthe oppositely-charged ions.
Na Cl Na
+Cl
-
Sodium atom, Na
2.8.1
Chlorine atom, Cl
2.8.7
Sodium ion,
2.8
Chlorides ion,
2.8.8
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FORMATION OF IONIC BOND
Example 2: Magnesium Chloride, MgCl2
Cl
MgCl
Cl Mg Cl
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EXAMPLE OF IONIC COMPOUND IN NATURE
Table salt ( NaCl ) Baking powder( NaHCO3 )
Sea shell ( CaCO3 )
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COVALENT BONDING
Covalent compound - Chemical compound
formed by sharing of valence electrons
between a non-metal with a non-metal atoms
Covalent molecules are held by weak inter-
molecular forces / van der Waals' forces.
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TYPES OF COVALENT BOND
There are 3 types of covalent bond:a)Single bond b)double bond c)triple bond
H2 O2 N2
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PHYSICAL PROPERTIES OF IONIC AND
COVALENT COMPOUNDS
Ionic Compound Covalent Compound
High melting and boiling points-Stronger attraction forces between the
ions
-more heat energy required toovercome the attraction forces
Low melting and boiling points-Weak intermolecular forces
/van der Waal’s forces between the
molecules- Less heat energy required to
overcome the weak intermolecular
forces
Conduct electricity in molten and
aqueous solution- Contains freely moving ions in
molten / aqueous state only
Does not conduct electricity
- consists of molecules- do not have freely moving ions.
Soluble in water but insoluble in
organic solvents
Insoluble in water but soluble in
organic solvents
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