Question

Mendeleev classified elements in:
[A] Increasing order of atomic groups.
[B] Seven periods and eight groups.
[C] Seven period and nine groups.
[D] Eight period and seven groups.

Answer 1

Hint: Mendeleev’s periodic table has 63 elements. They were placed in a tabular form in increasing order of their relative atomic masses. The table is divided into several rows and columns according to their atomic masses.

Complete step by step answer:
Dmitri Mendeleev was a Russian scientist and he arranged the 63 elements which were discovered till then in a tabular form in the order of their increasing relative masses. It is known as the Mendeleev’s periodic table.
The Mendeleev’s periodic Law states that “The properties of elements are the periodic function of their relative atomic masses.”
Now, let us discuss about the Mendeleev’s periodic table-
- The elements are arranged in increasing order of their atomic masses.
- The periodic table is divided into eight groups and seven periods.
- Group I to VII are normal elements and the group VIII is for transition elements.
- Group I to VII were divided into two sub-groups. Elements with similar properties are under same group. Like - lithium, potassium and rubidium etc. were put in the first group.
- Period fourth to seventh was divided into two series.
- Some blank spaces are left in his periodic table in order to place elements with similar properties.
We can understand from the above discussion that in his periodic table there were eight columns, known as groups and seven rows, known as periods.
So, the correct answer is “Option B”.

Note: There were certain limitations to Mendeleev’s periodic table.
- Hydrogen atoms make similar compounds like alkali metals so it was placed in the first group. But, it also exists as a diatomic molecule and makes covalent compounds like halogens. This anomaly was not explained.
- It had many elements placed in the incorrect order of increasing atomic masses in order to put them with the elements having similar properties.
- Placing isotopes in his periodic table was very difficult without changing the order of elements.