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mohd faisol mansor/chemistry form 4/chapter 4
56
Historical Development of Periodic Table
Johann Dobereiner
(1780 – 1849)
divided element
according their
similar chemical
properties
Antoine Lavoiser
(1743 – 1794)
first scientist classify
substances.
John Newlands
(1837 – 1898)
arranged element
in order of
increasing atomic
mass
Lothar Meyer
(1830 – 1895)
showing that the
properties of the elements
formed a periodic
pattern against their
atomic masses.
Dmitri Mendeleev
(1834 – 1907)
arranged the elements in
order of increasing atomic
mass and
grouped them
according to similar
chemical properties.
Henry J.G. Moseley
(1887 – 1915)
Studied the X-ray
spectrum of elements.
He rearranged the
elements in order of
increasing proton number.
Concluded that the
proton number should
be the basis for the
periodic change of
chemical properties
instead of the atomic
mass.
Leading to the modern
Periodic Table.
mohd faisol mansor/chemistry form 4/chapter 4
57
Arrangement of Element in the Periodic Table
Element in the
Periodic Table are
arranged in an
increasing order of
proton number
ranging 1 to 118.
Element with
similar chemical
properties are
placed in the same
vertical column
18 vertical column
called a group
7 horizontal rows
called a period
GROUP
The number of
valence electron in
an atom decides the
position of the group
of an element.
GROUP
Valence electron 1
and 2
GROUP
Valence electron 3
until 8
PERIOD
Equal to the number
of shell occupied
with electrons in its
atom
Example:
An atom of element X has a proton
number of 15. In which group and period
we can find element X in Periodic Table.
mohd faisol mansor/chemistry form 4/chapter 4
58
1. Element D has a proton number 19. Where is element D located in Periodic
Table?
2. An atom of element E has 10 neutrons. The nucleon number of element E is 19.
In which group and period of element E located in the Periodic Table?
3. An atom of element G has 3 shell occupied with electrons. It is placed in
Group 17 of the Periodic Table. What is the electron arrangement of atom G?
4. An atom Y is located in Group 18 and period 2 of the periodic Table. What is
the electron arrangement and proton number of atom Y?
5. Element R has a proton number of 11. Its atom has 6 neutrons. In which group
and period can you find element R in the Periodic Table?
Atom, Molecule & Ion
Exercise
mohd faisol mansor/chemistry form 4/chapter 4
59
The advantage of grouping elements in the Periodic Table
1. Helps us to study the element systematically especially their
physical and chemical properties.
2. Element with a same number valence electron is place in the
same group because they have the same chemical properties.
3. It could be used to predict undiscovered properties.
4. To relate the characteristic of an element with atomic structure
mohd faisol mansor/chemistry form 4/chapter 4
60
Physical Properties of Group 18
GROUP 18
consist of helium,
neon, argon,
krypton, xenon
and radon
GROUP 18
Known as
NOBLE GAS
Exist as
monoatomic gas.
GROUP 18
NOBLE GAS
COLOUR SOLUBILITY
ELECTRIC
CONDUCTIVITY
MELTING &
BOILING POINT
DENSITY
mohd faisol mansor/chemistry form 4/chapter 4
61
The inert properties of G18
All noble gas are inert which means unreactive.
Noble gas are inert because the outermost occupied shell are full.
This electron arrangements are very stable.
Helium have 2 valence electron, this electron arrangement is called
duplet electron arrangement whereas other noble gas have eight
valence electron which called octet electron arrangement.
p/s: All other element try to achieve noble gas electron arrangement to
become stable.
The Physical Properties of G18
The physical properties vary down the group.
physical properties vary down the group are related to atomic size.
Melting and boiling point of an element increase when going
down the group because the atomic sizes increase, the forces
attraction (Van der Waals forces) becomes stronger. Thus more
heat energy is required to overcome the forces.
The strength of Van der Waals forces propotional to the size of
particle
mohd faisol mansor/chemistry form 4/chapter 4
62
Uses of Noble Gas Elements
Fill light bulb laser for repair retina,
photographic flash lamps
fill airships and weather
balloons
treatment cancer
advertising light and
television tubes
Car bulb, use in bubble chamber
[ State the element of group 18 ]
mohd faisol mansor/chemistry form 4/chapter 4
63
1. Table below shows the electron arrangements of atoms of elements P, Q,
and R.
Element Electron Arrangement
P 2.8
Q 2.8.18.8
R 2.8.18.32.18.8
a) Arrange the element in ascending order of boiling points. Give reasons for
your answer.
b) Elements P, Q, and R are chemically unreactive. Why?
2) What is the meaning of
a) Duplet electron arrangement
b) Octet electron arrangement
Exercise
mohd faisol mansor/chemistry form 4/chapter 4
64
Physical Properties of Group 1
GROUP 1
Known as Alkali
Metals.
Have valence
electron of 1.
Consist of elements
such as lithium,
sodium, potassium,
rubidium, caesium
and francium.
GROUP 1
ALKALI
METALS
HARDNESS APPEARANCE
ELECTRIC
CONDUCTIVITY
MELTING
POINT
DENSITY
mohd faisol mansor/chemistry form 4/chapter 4
65
A melting point of a metal indicates the strength of its metallic bonding in its
structure.
Generally, the strength of metallic bonding is directly proportional to the number
of valence electron per atom divided by the radius of a metal.
A metallic bond can be defined as the electrostatic force between the
positively charged metallic ions and the ‘sea’ of electrons.
Electropositivity is the measurement of an atom to release an electron and form
positive ion
When going down the group, what happen to the electropositivity of the
element? Why?
Element Atomic Size
Melting /
Boiling
point
Density Hardness
Lithium
Sodium
Potassium
Rubidium
Caesium
Francium
mohd faisol mansor/chemistry form 4/chapter 4
66
Chemical Properties of Group 1 Elements
Exercise :
1. Why does Group 1 element have similar chemical properties?
2. Why is paraffin oil used to store metals such as sodium and potassium?
3. Element in Group 1 has similar chemical properties but differ in reactivity.
Why?
React vigorously with water to produce alkaline metal hydroxide solution
and hydrogen gas, H2.
2Li (s) + 2H2O 2LiOH (aq) + H2 (g)
Burn in oxygen gas rapidly to produce solid metal oxide
4Li (s) + O2 (g) 2 Li2O (s)
Solid metal oxide dissolve in water to form alkaline metal hydroxide
Li2O (s) + H2O 2LiOH (aq)
Alkaline metal burn in chlorine gas, Cl2 to form white solid metal chloride
2Na (s) + Cl2 2NaCl (aq)
mohd faisol mansor/chemistry form 4/chapter 4
67
To investigate the chemical properties of Lithium, Sodium & Potassium
[ Discussion ]
1. Why are the experiments involving sodium and potassium demonstrated by
your teacher and not carried out by the students?
2. Write the chemical equations for the reactions of lithium, sodium and
potassium with
a) Water, H2O
Lithium :
Sodium :
Potassium :
b) Oxygen gas, O2
Lithium :
Sodium :
Potassium :
[ Draw the diagram ]
1) The reaction of alkali metals with water
2) The reaction of alkali metals with O2 gas
[ Draw the diagram ]
mohd faisol mansor/chemistry form 4/chapter 4
68
3. Write the chemical equations for the reactions between the products from
the combustion of each alkali metal with water.
Lithium :
Sodium :
Potassium :
1. A student performs two experiments to study the reaction of alkali metal with
water.
Experiment Metal used Observation
1 Sodium Sodium moves rapidly and randomly on the
water surface and emits ‘hiss’ sounds.
2 Lithium Lithium moves slowly on the water surface.
a) Write the chemical equation for the reaction between sodium and lithium
with water.
Lithium :
Sodium :
b) Between reactions of Experiment 1 and 2, which is more vigorous? Explain
your answer from the point of electron arrangement.
c) Explain why sodium and lithium show similar chemical properties?
d) Calculate the volume of hydrogen gas produced if 2.3 g of sodium is used.
[RAM: Na, 23 ; molar volume: 24 dm3 mol-1]
Exercise
mohd faisol mansor/chemistry form 4/chapter 4
69
GROUP 17
consist of fluorine,
chlorine, bromine,
iodine and
astatine.
GROUP 17
Known as
HALOGENS.
Have valence
electron of 7.
GROUP 17
Elements are
poisonous.
Exist as diatomic
molecules.
Element Symbol of
Atom
Symbol of
Molecule
Physical
state at
room
condition
Colour
Fluorine
Chlorine
Bromine
Iodine
Astatine
Physical State
HALOGENS
Melting & Boiling
Point Electric
Conductivity
Density
Smell
mohd faisol mansor/chemistry form 4/chapter 4
70
Electronegativity is an ability of atom to receive an electron to become
negative charged ions.
All halogen have seven valence electron. Their atoms always gain one electron
to form an ion with a charge of –1, in order to achieve stable octet electron
arrangement.
Chemical Properties of Group 17 Elements
Element Atomic
Size
Melting /
Boiling
point
Density Electronegativity
Fluorine
Chlorine
Bromine
Iodine
Astatine
Halogen react with water to produce two acids
Cl2 + H2O HCl + HOCl
Halogen react with metal to produce metal halides
2Fe (s) + 3Cl2 (g) FeCl3 (s)
Halogen react with sodium hydroxide solution to form sodium
halide and sodium halate (I) and water
I2(s) + 2NaOH (aq) NaI (aq) + NaOI (aq) + H2O (l)
mohd faisol mansor/chemistry form 4/chapter 4
71
To Investigate the Chemical Properties of Halogens
[Draw the Apparatus]
SECTION A : Reaction with Water
1) Chlorine
2) Bromine 3) Iodine
SECTION B : Reaction with Iron
1) Chlorine
2) Bromine 3) Iodine
SECTION C : Reaction with Sodium Hydroxide
1) Chlorine
2) Bromine 3) Iodine
mohd faisol mansor/chemistry form 4/chapter 4
72
[Discussion]
1. Name the products formed when chlorine, bromine, and iodine
react with water.
Chlorine :
Bromine :
Iodine :
2. Write the chemical equations for the reaction of chlorine,
bromine and iodine with water.
Chlorine :
Bromine :
Iodine :
3. What is the function of soda lime in SECTION B?
4. Name the products formed when chlorine, bromine, and iodine
react with iron.
Chlorine :
Bromine :
Iodine :
5. Write the chemical equation for the reaction of chlorine,
bromine, and iodine with iron.
Chlorine :
Bromine :
Iodine :
mohd faisol mansor/chemistry form 4/chapter 4
73
4. Name the products formed when chlorine, bromine, and iodine
react with sodium hydroxide solution.
Chlorine :
Bromine :
Iodine :
5. Write the chemical equation for the reaction of chlorine,
bromine, and iodine with sodium hydroxide solution.
Chlorine :
Bromine :
Iodine :
6. Describe the changes in reactivity of Group 17 elements when
going down the group. Explain your answer.
mohd faisol mansor/chemistry form 4/chapter 4
74
1. Table below shows several halogen elements with their proton numbers.
Halogen Proton Number
X 9
Y 17
Z 35
a) State the group that the halogen elements belong to in the Periodic Table.
b) i) Write the electron arrangement of elements X and Y.
ii) From your answers in (b)(i), deduce the period of elements X and Y.
c) Draw the electron arrangement of element Y.
d) State the changes of properties of halogens down the group from X to Z in
terms of:
i) Atomic radius
ii) Electronegativity
iii) Melting point and boiling point
Exercise
mohd faisol mansor/chemistry form 4/chapter 4
75
e) i) Iron glow brightly when reacting with element Y. Write the chemical
reaction to represent this reaction.
ii) Predict the observation for the reaction between iron and element Z.
iii) Between Y and Z, which is more reactive? Explain why.
f) i) Determine the elements X, Y and Z.
ii) State the colour for each elements X, Y, and Z.
iii) Why the physical state of halogen differ when down the group?
mohd faisol mansor/chemistry form 4/chapter 4
76
Comparison & Similarities between Group 1 and Group 17
Properties Group Down the Group
Atomic
Size
1
17
Melting &
Boiling
Point
1
17
Density 1
17
Reactivity 1
17
mohd faisol mansor/chemistry form 4/chapter 4
77
Elements in a Period 3
Element Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon
Symbol
Proton Number
Electron
Arrangement
Metal Properties
Physical State
[RC]
Atomic Radius
Electronegativity
Property of the
oxide
Note: the atomic radius ______________ and electro negativity ______________
due to the increasing nuclei attraction on the valence electrons.
(nuclei attraction force increase with the increase of proton number)
The proton number ____________ by one unit.
All atom of the element have __________ shells occupied by electron.
The number of valence electron ____________ from 1 to 8.
All element exist as __________ except chlorine and argon.
The atomic radius of element ________________.
The electronegativity of element ______________.
The oxides of element in Period 3 change from basic to acidic properties,
therefore the metallic properties decrease across the period. On the other
hand non-metallic properties of the elements increase.
mohd faisol mansor/chemistry form 4/chapter 4
78
Transition Elements
Transition elements are elements from Group 3 to Group 12
All the elements are metals, usually solids with shiny surfaces, ductile,
malleable and have tensile strength.
Have high melting and boiling point as well as high density.
Good conductors of heat and electricity.
Three special characteristics of transition element
Show different oxidation number in their compound.
Form coloured ions or compound.
Act as catalysts.