Additional Questions With Solutions

Question 1. Write the main features of Mendeleev's periodic table.

Answer: Mendeleev arranged the elements in a horizontal row in the order of their increasing atomic mass. Elements with similar properties were placed in all the vertical pillars. Following are the main features of this table:-

(a) Groups and Subgroups:- There are 8 groups in the periodic table. Groups I to VII are divided into two subgroups.

(b) The number of periods in the periodic table is 7 which are known as 1,2,3,4,5,6 and 7.

1st period - 2 elements

Second Period - 8 Elements

Third Period - 8 Elements

Fourth Period - 18 Elements

Fifth Period - 18 Elements

Sixth Period - 32 Elements

seventh period - incomplete period

Question 2: Write some characteristic features of the periodic table.

Answer: Some of the distinctive features of the periodic table are as follows:-

(i) Elements are placed in a special way in groups and periods than before.

(ii) The properties of many elements were inferred from this type of classification.

(iii) The atomic masses of many elements were modified.

(iv) The possibility of discovery of new elements increased and new elements were also discovered.

Question 3 - Differentiate between modern periodic table and Mendeleev's periodic table.
Answer -
Modern periodic table
1. Elements are arranged in increasing atomic number.
2. This periodic table has 18 vertical columns and 7 horizontal rows.
3. Isotopes of elements are placed at the same place as their corresponding elements because they have the same atomic number.
4. Chemically dissimilar elements are kept in separate groups.
Mendeleev's periodic table
1. Elements are arranged in increasing atomic masses.
2. This periodic table has 8 vertical columns and 6 horizontal rows.
3. The isotopes of the elements are not found in proper positions.
4. Chemically dissimilar elements held together.