chapter 4 chemical bonding

1.1

INTRODUCTION

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Chemical bonding – the force of attraction between the two atoms

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Valence electron – the outer most shell electrons

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There are three types of chemical bonding
i.

Ionic bond: ________________________________________

ii.

Covalent bond: _____________________________________

iii.

Dative Covalent bond: _______________________________

1.1.1 LEWIS DOT SYMBOL
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A shorthand to represent the valence electron of an atom.
The element symbol surrounded by dots that represent the valence electrons.
The Lewis structures for the certain elements in the second periods of the periodic table are shown below.

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Lewis structures can also be used to show bonding between atoms. o The bonding electrons are placed between the atoms and can be represented by a pair of dots or a dash (each dash represents one pair of electrons, or one bond). Eg: Lewis structures for H2 and O2.

1

FGS 0064 Chemistry I
Center for Foundation Studies (CFS)

1.1.2 THE OCTET RULE
The atoms of the representative elements form bonds to obtain 8 valence electrons. Atoms achieve noble configuration by transferring of electrons or sharing electrons.

1.2
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IONIC BONDING
Exist between Metal + Non metal
Formed by the transferring of electrons from metal atom to non metal atom
Formation of oppositely charged cation and anion → the two ions held together by strong electrostatic force (ionic bond)
Metal loses its valence e → cation
Non – metal gains e → anion
Eg : Formation of NaCl, MgBr2

1.2.1 PROPERTIES OF IONIC COMPOUNDS
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The ions occupy fixed positions in the ionic lattice
They can conduct electricity (in melting state or in a solution phase)
High melting and boiling points
Rarely soluble in organic solvents
Water-soluble

2

FGS 0064 Chemistry I
Center for Foundation Studies (CFS)

Exercise
Use Lewis dot symbols to show the formation of the following ionic