This document summarizes the history and development of the periodic table. It discusses early scientists like Lavoisier who first classified elements, Dobereiner who grouped elements into triads, and Newlands who saw a periodic pattern. Meyer and Mendeleev created early periodic tables that grouped elements by properties and left spaces for undiscovered elements. Moseley later determined that atomic number, not mass, was the basis for the recurring properties and rearranged the periodic table accordingly. The modern periodic table arranges elements in order of increasing proton number, with elements of similar properties in the same group and period based on electron configuration.

2. 
Henry J.G.MOseley
Dmitri Mendeleev
Lothar Meyer
John Newlands
Johann
Dobereiner
Antoine
Lavoisier
HISTORY

3. 
 1789, classify substances including light and
heat, into metals and non metals.
 Unsuccessful because light, heat and a few
other compounds were also considered as
elements.
Antoine Lavoisier

4. 
 1829, divide the elements into groups of 3 elements
with similar chemical properties, known as
Dobereiner’s triads.
 Atomic mass of the middle elements was
approximately the average atomic mass of the other
2 elements in each triad.
 There was a relationship between the chemical
properties and the atomic mass of each elements.
Johann Dobereiner

5. 
 1864 – 1865, arrange the known elements in order
of increasing atomic mass. Elements with similar
properties recurred at every 8 elements, known
as the law of Octaves.
 Failure because the Law of Octaves was obeyed
by the first 17 elements only.
 Show the existence of a periodic pattern for
the properties of elements.
John Newlands

6. 
 1870, plotted a graph of the atomic volume against
of the atomic mass for all the known elements.
 Realised that elements with similar chemical
properties occupied equivalent positions on the
curve.
 Show that the properties of the elements formed a
periodic pattern against their atomic masses.
Lothar Meyer

7. 
 1869, arrange the elements in order of
increasing atomic mass and grouped them
according to similar chemical properties.
 He left gaps in the table to be filled by
undiscovered elements.
 Able to predict the properties of undiscovered
elements.
Dmitri Mendeleev

8. 
 1949, studied the x-ray spectrum of elements.
 Concluded that proton number should be the
basis for the periodic change of chemical
properties instead of the atomic mass.
 Rearranged the elements in order of increasing
proton number in the Periodic Table. Thus,
confirmed the works of Mendeleev.
Henry J.G.
Moseley

9. 
 Arrange in increasing order of proton number.
(ranging from 1 to 113)
 Elements with similar chemical properties are placed
in the same vertical column.
• Each vertical column of elements is called a group. (Group
1 to Group 18)
• Horizontal row of elements in the table is called Period
 The Group and Period of an element can be known by
the electron arrangement :
• Number of valance electron : Position of the group
• Number of shells : Position of period
ARRANGEMENT OF
ELEMENTS

10. 
X
13
 electron arrangement : 2.8.3
 Group : Group 13 and Period : 3
example :

11. 
PERIODIC TABLE

12. 
Q & A
(objective questions)

13. 
Who is the scientist that classify the elements
with the same chemical properties into a groups
called triads ??
A. Dmitri Mendeleev
B. John Newlands
C. Antoine Lavoisier
D. Johann Dobereiner
answer: D
Question 1

14. 
Who was the scientist that left gaps in the
periodic table for elements which were not known
at that time ??
A. John Newlands
B. Dmitri Mendeleev
C. Lothar Meyer
D. Henry J.G Moseley
answer: B
Question 2

15. 
In the periodic table, S is below T in the same
group. If the proton number of T is 12, what is the
electron arrangement of S ??
A. 2.2
B. 2.8.3
C. 2.8.8.2
D. 2.8.8.4
answer: c
Question 3

16. 
 Textbook Chemistry Form 4
 http://www.slideshare.net/faridahhamat/chapte
r-4-perodic-table
REFERENCE

17. 
special thanks to all
Chemistry TEACHERS
!!!
CHEMISTRY A +