chemistry chapter 5 form 4

8/10/2019 Chemistry chapter 5 form 4

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CHAPTER 5 :

CHEMICAL BONDS

1



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



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.



Mg

2.8.2 2.8

Magnesium atom Magnesium ion

donates 2 electrons

Mg

2+

ELECTRON ARRANGEMENTS

FOR THE IONS FORMED



ELECTRON ARRANGEMENTS

FOR THE IONS FORMED

2.8.72.8.8

ClCl

-

Chlorine atom Chloride ion

accepts 1 electron

+



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



FORMATION OF IONIC BOND

Example 2: Magnesium Chloride, MgCl2

Cl

MgCl

Cl Mg Cl



EXAMPLE OF IONIC COMPOUND IN NATURE

Table salt ( NaCl ) Baking powder( NaHCO3 )

Sea shell ( CaCO3 )



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.



TYPES OF COVALENT BOND

There are 3 types of covalent bond:a)Single bond b)double bond c)triple bond

H2 O2 N2



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

chemistry chapter 5 form 4

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