MENDELEEV’S Periodic Law:
In 1869 Mendeleev’s first published the periodic
system of element on the basis of
periodic law. According to this law physical and chemical properties of
elements are functions of their atomic masses”.
“The
properties of elements are periodic
functions of their atomic masses”
He
arranged the 63 known elements in the periodic table horizontally in the order
of the their similarities in properties. The horizontal rows are called periods
and verticals columns groups.
Main Characteristic
of Mendeleev’s periodic Table
·
Mendeleev’s excluded certain elements and assigned them a separate
position.
·
Some chemically similar elements had been placed differently for e.g.,
Cu, & Hg , Ag, and Te and Ba and Pb.
·
Left gaps for the then undiscovered elements.
·
The order of atomic mass in reverse in some elements (a) Co(58.9)
precedes Ni(58.6) (b) Ar(39.9) precedes K(39.1)
·
The properties of the elements vary gradually and get repeated at
intervals 2.8.8.18.18.and 32 elements respectively.
·
Position of hydrogen is not clear. It demands its position on 1st
group as well in 7th group.
·
Some chemically dissimilar elements have been placed in the same group
for e.g. alkali metals (Li,Na,K—) of subgroup IA and coinage metals (Cu, Ag,
Au, )of sub group IB are placed in group 1st.
·
Predicted the existence of some undiscovered elements
·
Isotopes have no place in this periodic table.
Instruction: Separate advantages (merits ) and disadvantages(demerits)
of Mendeleev’s periodic from above information
|
Advantages(Merits)
|
Disadvantages(Demerits)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
