Ionic Bonding

advertisement

Formation of compounds

What happens when a piece of burning sodium is placed in a gas jar of chlorine?

+ sodium chlorine sodium chloride

Before Bonding

Na

Cl sodium = 11 electrons :

2, 8, 1 chlorine = 17 electrons :

2, 8, 7

Sodium gives 1 electron to chlorine

Na

Cl sodium ion

Charge

11 protons

10 electrons

+ 1

Na + = 2 , 8 chloride ion

Charge

17 protons

18 electrons

- 1

Cl = 2, 8, 8

After Bonding

Na Cl

This type of bonding is known as ionic bonding because the metal atoms transfer electron(s) to non-metal atoms and ions are formed.

Sodium atom loses an electron to form sodium ion Na +

Chlorine atom gains an electron to form chloride ion

Cl -

Chemical formula of sodium chloride is NaCl

When metal meet non-metals, the sparks will fly

Give me the electrons!” non-metal do cry

“you got a deal!” the metal responds

The ions attract to form their bonds.

Lithium + fluorine

 lithium fluoride

Before Bonding

Li

F lithium = 3 electrons :

2, 1 fluorine = 9 electrons :

2, 7

Lithium gives 1 electron to fluorine

Li

F lithium ion

Charge

3 protons

2 electrons

+ 1

Li + = 2 fluoride ion

Charge

9 protons

10 electrons

- 1

F = 2, 8

After Bonding

Li

F

Lithium atom loses an electron to form lithium ion Li +

Fluorine atom gains an electron to form fluoride ion F

-

Chemical formula of lithium fluoride is LiF

What happens when a piece of magnesium is burnt in air?

magnesium + oxygen  magnesium oxide

Before Bonding

Mg

O magnesium = 12 electrons :

2, 8, 2 oxygen = 8 electrons :

2, 6

Magnesium gives 2 electrons to oxygen

2 +

2 -

Mg

O magnesium ion

12 protons

Charge

10 electrons

+ 2

Mg 2+ = 2 , 8 oxide ion

Charge

8 protons

10 electrons

- 2

O 2= 2, 8

After Bonding

2 +

Mg

2 -

O

Magnesium atoms lose 2 electrons to form magnesium ions Mg 2+

Oxygen atoms gain 2 electrons to form oxide ions O 2-

Chemical formula of magnesium oxide is MgO

Mg

Mg = 12 electrons:

2, 8, 2

Cl = 17 electrons : 2, 8, 7

Cl

Cl

Mg

Mg 2+

= 2 , 8

Cl -

= 2 , 8, 8

2 +

Cl

Cl

After Bonding

Mg

2 +

2 Cl

Magnesium lost 2 electrons to form magnesium ions Mg 2+

Each chlorine atom gained an electron to form chloride ions Cl –

Magnesium chloride is MgCl

2

Sodium oxide

Na

Na: 11 electrons :

2, 8, 1

Na

O

O : 8 electrons :

2, 6

Na

Na + = 2 , 8

O 2= 2, 8

Na

O

2-

After Bonding

2

Na

O

Each sodium atom lost an electron to form sodium ions Na +

An oxygen atom gained 2 electrons to form an oxide ion O 2-

Sodium oxide is Na

2

O

2-

K

Potassium sulphide

S

S : 16 electrons :

2, 8, 6

K: 19 electrons :

2, 8, 8, 1

K

S

2-

K

K + : 2, 8, 8

K

S 2: 2, 8, 8

After Bonding

2 K

S

Each potassium atom lost an electron to form potassium ions K +

A sulphur atom gained 2 electrons to form sulphide ion S 2-

Potassium sulphide is K

2

S

2-

Al = 13 electrons:

2, 8, 3

Al

F

F

F

F = 9 electrons : 2, 7

Al 3+ : 2, 8

Al

3 +

F

F

F

F : 2, 8

After Bonding

Al

3 +

3

F

Aluminium atom lost 3 electrons to form aluminium ions Al 3+

Each fluorine atom gained an electrons to form fluoride ion F

Aluminium Fluoride is AlF

3

Summary

Li

Na Mg

K Ca

Al

O F

S Cl

Metals transfer electrons to non-metal forming ions

Predict the formulas for the following ionic compounds:

Potassium bromide KBr

Lithium oxide Li

2

O

Magnesium sulphide MgS

Sodium iodide Na I

Aluminium chloride

AlCl

3

Calcium fluoride CaF

2

Download