Question

Compare Dobereiner’s triads to the modern periodic table. What aspects of his idea agreed with the modern table and what aspects did not

Answer 1

Answer:

In  Dobereiner’s triads, elements were placed :

• According to increasing order of their atomic masses.
• Into groups which have similar chemical and physical properties.
• In each group there were three elements.

In Modern periodic table, elements are placed:

• According to increasing order of their atomic numbers.
• Into groups and these groups are assigned according to the numbers of valence electrons present in their valence shell.

Aspects of Dobereiner’s triads agreed with the modern periodic table

• Element of the same group will have similar chemical and physical properties.

Disagreement with the modern periodic table.

• Not all groups obeyed law of triads.
• On the basis of properties all known elements could not be classified into groups of triads.