Question

Before modern periodic law, the classification of elements was done on the basis of which property?

• A. (a) Atomic number
• B. (b) Atomic radius
• C. (c) Number of electrons
• D. (d) Atomic mass

Answer 1

The correct option is D

(d) Atomic mass

Part 1: Explanation for correct answer:-

Option (d) Atomic mass:-

1. Before the modern periodic law, Mendeleev's periodic law was followed.
2. According to Mendeleev's periodic law, the classification of elements was done on the basis of their atomic masses.

Part 2: Explanation for incorrect answer:-

Option (a) atomic number:-

1. In the modern periodic law, the elements were a periodic function of atomic number of the elements, not the in the Mendeleev's periodic law
2. Hence option is incorrect.

Option (b) atomic radius:-

1. Before modern periodic law, the elements were a function of atomic masses of the elements, not their atomic radius.
2. Hence option is incorrect.

Option (c) number of electrons:-

1. Before modern periodic law, the elements were a function of atomic masses of the elements, not their number of electrons.
2. Hence option is incorrect.

Hence, Before modern periodic law, the classification of elements was done on the basis of option (d) Atomic mass.