Question

CHEMISTRY
PROJECT WORK (CLASS IX)
1. write on Study of developments in periodic table.​

Answer 1

Answer:

In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them. In 1886 French physicist Antoine Bequerel first discovered radioactivity