Question

describe the main features of mendeleev periodic table

Answer 1

  Ans: According to Mendeleev’s Periodic Law  “The Physical and Chemical Properties of the elements are the periodic functions of their atomic weights.”
     
Mendeleev classified periodic table into horizontal rows and vertical coloumns. The horizontal rows are called as periods and vertical columns are called groups.
The elements with similar properties comes into same group.
 Mendeleev also left gaps in his periodic table for undiscovered elements like aluminum, silicon and Boron in his periodic table and named them Eka-Aluminium, Eka-silicon and Eka-Boron.
  Mendeleev not only predicted the existence of Eka-Aluminium, Eka-silicon and Eka-Boron but also described the general physical properties of these elements.
These elements discovered later and named as Gallium, Germanium and Scandium.
Even though, Mendeleev’s periodic table has certain drawbacks.
Drawbacks of Mendeleev’s Periodic Table:
a.       Concerns about the position of hydrogen.
b.      No place for the isotopes of elements in the periodic table.
c.       The placement of element having greater atomic mass before the elements having lower atomic mass could not be logically explained.

hope this helps you dear

Answer 2

Mendeleev's Periodic table .

→ When Mendeleev started his work , 63 elements were known at that time .

→ He examined the relationship between the atomic masses of the elements and their physical and chemical properties .

→  Mendeleev concentrated on the compounds formed by elements with oxygen and hydrogen .

Classification criteria :-

1. The formulae of the hydrides and oxides formed by an element were treated as one of the basic properties of an element foe its classification.

2. He then took 63 cards and on each cards he wrote down the properties of one element. He sorted out the elements with similar properties and pinned the cards todether on the wall .He observed that most of the elements got a place in the periodic table and were arranged in the order of increasing atomic masses .

On this basis , Mendeleev formulated a periodic law .

→ Which states that " The properties of elements are the periodic function of their atomic masses .

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