EVOLUTION OF PERIODIC TABLE

2. • First attempt to classify elements
• Classified 30 elements then known into metals
and non metals

3. Classified elements as
triads

4. Classification of John Newlands
In 1863, he suggested that elements be arranged in “octaves” because he noticed
(after arranging the elements in order of increasing atomic mass) that certain
properties repeated every 8th element.
1838 - 1898
Law of Octaves

5. Newland’s law of octaves [John
Newland (1862)]
Element
Atomic mass
Element
Atomic mass
Element
Atomic mass
I II III IV V VI VII
Li Be B C N O F
7 9 11 12 14 16 19
Na Mg Al Si p S Cl
23 24 27 28 31 32 35.5
K Ca
39 40

6. Dmitri Mendeleev (1869)
In 1869 Mendeleev and Lothar Meyer (Germany)
published nearly identical classification schemes for
elements known to date. The periodic table is base on
the similarity of properties and reactivities exhibited by
certain elements

7. MODERN PERIODIC TABLE
Henri Moseley ( England,1887-1915)
established that each elements has a
unique atomic number, which is how
the current periodic table is organized.