Question

What are the main features of Mendeleev's periodic table

Answer 1

Answer:

Mendeleev arranged the elements in horizontal rows (known as periods) in the increasing order of their atomic masses. Each vertical column (called groups) contained elements of similar properties. The main features of Mendeleev's periodic table are:

Groups and sub-groups: There are eight groups (I to VIII). Zero group was not present. With the exception of group VIII, each of the remaining groups are sub-divided into sub-groups A and B.

Periods: Horizontal rows are called periods. There are six periods numbered as 1, 2, 3, 4, 5, and 6. The number of elements in each period are:

1st period—2 elements

2nd period and 3rd period—8 elements each (short period)

4th period and 5th period—18 elements each (long period)

6th period—32 elements including 14 rare earth

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Answer 2

Mendeleev's periodic Table

♦ Mendeleev's periodic table contains vertical columns called 'groups' and horizontal rows call 'periods'.

♦ There are in all eight groups, i.e., group I to group VIII. Each of these groups from I to VII is divided into two sub-groups : A and B. Group VIII has no sub group. Inert gases were not known at that time.

♦ All elements of a sub-group ( or of the group VIII, which has no sub-group) have similar properties and show the same valency, which is equal to the group number ( for upto Group IV ) or group number subtracted from eight ( for Groups V-VII ).

♦ In a period, elements gradually change from metallic to a non-metallic character or metallic character decreases as one moves from left to right across the horizontal row.

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