SCIENCE CLASS

1 of 36 © Boardworks Ltd 2006

Science Class

CHECKING OF ATTENDANCE
OBJECTIVES:

 Illustrate how an ionic bond is

formed.
 Show how an ions are
formed.
 KEY QUESTIONS
Why do have to study
chemical bonding?

What keeps you bonded

with others?
 REVIEW
What are the four types
of quantum number?
How are electrons occupy
orbitals according to
AufbauPrinciple?
6
Chemical Bonding

IV
Chemical Bond

 A bond results from the attraction of

nuclei for electrons
– All atoms trying to achieve a stable octet
– a force that holds groups of two or more
atoms together and makes them function as
a unit.
 IN OTHER WORDS
– the p+ in one nucleus are attracted to the e-
of another atom
 Electronegativity
Octet Rule = atoms tend to gain, lose or share electrons so
as to have 8 electrons
C would like to Gain 4 electrons
N would like to Gain 3 electrons
O would like to Gain 2 electrons
 Lewis Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell
electrons

1 2 13 14 15 16 17 18
H He:
      

Li Be B   C  N  O : F  :Ne :

    

      

Na Mg  Al  Si  P S :Cl  :Ar :

    
Chemical bonds: an attempt to fill electron shells

TYPES OF CHEMICAL
BONDING
1. Ionic bonds –
2. Covalent bonds –
3. Metallic bonds
 Learning Check

1. X would be the
electron dot formula for
a.) Na b.) K c.) Al
 Learning Check


2.  X  would be the electron dot
formula for

a.) B b.) N c.) O
IONIC BOND
bond formed between
two ions by the transfer
of electrons
Ionic Bond

 Ionic
Bond: a total transfer of
one or more electrons from one
atom to another
Ionic compounds form into
crystals of repeating formula
units
Ionic bonds are extremely strong
Ionic Bond

 Reactions between metals and

nonmetals (representative) tend
to form ionic bonds
A positively charged ion (CATION) is
attracted to a negatively charged ion
(ANION)—attraction between ions is
due to their opposite charges
Example: Na+ + Cl-  NaCl
IONic Bonding
 electrons are transferred between
valence shells of atoms
 ionic compounds are NOT MOLECULES
made of ions

• ionic compounds are called Salts or

Crystals
IONic bonding
 Alwaysformed between metals
and non-metals

[METALS ]
+ [NON-METALS ]
-

Lost e- Gained e-
 Formation of Ions from Metals

Ionic compounds result when

metals react with nonmetals
Metals lose electrons to match
the number of valence electrons of
their nearest noble gas
 Formation of Ions from Metals

Positive ions form when the number

of electrons are less than the number
of protons
Group 1 metals  ion 1+
Group 2 metals  ion 2+
Group 13 metals  ion 3+
 Formation of Sodium Ion

Sodium atom Sodium ion

Na  – e  Na +
2)8)1) 2)8) ( = Ne)

11 p+ 11 p+
11 e- 10 e-
0 1+
 Formation of Magnesium Ion

Magnesium atom Magnesium ion


Mg  – 2e  Mg2+

2)8)2 2)8 (=Ne)

12 p+ 12 p+
12 e- 10 e-
0 2+
 Some Typical Ions with Positive
Charges (Cations)

Group 1 Group 2 Group 13

H+ Mg2+ Al3+
Li+ Ca2+
Na+ Sr2+
K+ Ba2+
 Learning Check

1. Number of valence electrons in

aluminum
A.) 1 e- B) 2 e- C) 3 e-

2. Change in electrons for octet

A.) lose 3e- B.) gain 3 e- C.)gain 5 e-
 Learning Check

3. Ionic charge of aluminum

A.) 3- B.) 5- C.) 3+
 Learning Check

Give the ionic charge for each of the

following:
1.) 12 p+ and 10 e-
A.) 0 B.) 2+ C.) 2-
2.) 50p+ and 46 e-
A.) 2+ B.) 4+ C.) 4-
 Learning Check

Give the ionic charge for each of the

following:
3.) 15 p+ and 18e-
A.) 3+ B.) 3- C.) 5-
 Ions from Nonmetal Ions

In ionic compounds, nonmetals

in 15, 16, and 17 gain electrons
from metals
 Ions from Nonmetal Ions

Nonmetal add electrons to

achieve the octet arrangement

Nonmetal ionic charge:

3-, 2-, or 1-
 Fluoride Ion

unpaired electron octet

  1 -
:F + e : F:
 

2)7 2)8 (= Ne)

9 p+ 9 p+
9 e- 10 e-
0 1-
ionic charge
 Ionic Bond
• Between atoms of metals and nonmetals
with very different electronegativity
• Bond formed by transfer of electrons
• Produce charged ions all states.
Conductors and have high melting point.
• Examples; NaCl, CaCl2, K2O
Ionic Bonds: One Big Greedy Thief Dog!
 Ionic bond – electron from Na is transferred to
Cl, this causes a charge imbalance in each atom.
Na becomes (Na+) and Cl becomes (Cl-),
charged particles or ions.
In an IONIC bond, electrons are lost or
gained,resulting in the formation of IONS in
ionic compounds.

K F
K F
K F
K F
 +
_
K F
 +
_

K F
The compound potassium
fluoride consists of potassium
+ -
(K ) ions and fluoride (F ) ions
Example:
Show the bond formation using the Lewis electron
dot between Lithium and Fluorine

. ..
Li. + :F:  Li+ : F - :
.. ..
Check Your Understanding

Use Lewis Electron Dot Diagram

to show the bond formation
between the following elements:
1. Magnesium and iodine
2. Sodium and sulfur
3. Calcium and oxygen
 Properties of Ionic Compounds
SALTS
 Low conductivity Crystals

Conductivity - is the measure of the

ease at which an electric charge or
heat can pass through a material.
 nonconductors of electricity in solid
phase
 good conductors in liquid phase or
dissolved in water (aq)
 Properties of Ionic Compounds
SALTS
Crystals

 These are hard, because of the

crystalline nature.

Hardness - is the resistance of a material

to deformation of an indenter of specific
size and shape under a known load
 Properties of Ionic Compounds
SALTS
Crystals
 High boiling point and melting
point
Melting and Boiling Points – The boiling point is
the temperature at which a material changes from
a liquid to a gas (boils) while the melting point is
the temperature at which a material changes from
a solid to a liquid (melts). Keep in mind that a
material's melting point is the same as its freezing
point
 Properties of Ionic Compounds
SALTS
Crystals
 Non-malleable

Malleability - the state of being

shaped, as by hammering or
pressing into thin sheets
 Properties of Ionic Compounds
SALTS
Crystals
 Non-ductile

Ductility - the capacity to

undergo a change of physical
form without breaking
 Properties of Ionic Compounds
SALTS
Crystals
 Low volatile
Volatility - tendency of a substance
to evaporate at normal
temperatures.
 Properties of Ionic Compounds
SALTS
Crystals
 Usually insoluble in water but soluble in
organic solvents such as ether, alcohol,
benzene, tetrachloromethane, propanone
and other.
Solubility - is a property referring to
the ability for a given substance,
the solute, to dissolve in a
solvent.
 CHECK YOUR UNDERSTANDING

1. Bonds between metals and other nonmetals are

generally _______________

A. Covalent bond
B. Metallic bond
C. Ionic bond
D. Polar covalent bond
 CHECK YOUR UNDERSTANDING

2. When atoms transfer valence electrons, a(an) _____

is formed.

A. Covalent bond
B. Metallic bond
C. Ionic bond
D. Polar covalent bond
 CHECK YOUR UNDERSTANDING

3. Which of the following is NOT a characteristics of

ionic compounds?

A. Low conductivity
B. Non-malleable
C. High melting point
D. Highly volatile
 CHECK YOUR UNDERSTANDING

4. Non-metals form _______ because

they attract electrons toward themselves?
A. Cation
B. Ion
C. Anion
 CHECK YOUR UNDERSTANDING

5.Metals form _______ because they

completely transfer or give away electrons?
A. Cation
B. Ion
C. Anion
 VALUES INTEGRATION

DO YOU BELIEVE IN THE

SAYING “ IT IS BETTER TO
GIVE THAN TO RECEIVE?
WHY?