Question

Explain correctness and usefulness of Mendeleev periodic table with example eka-aluminium

Answer 1

1)To give the proper place in the periodic table, atomic masses of some elements were revised in accordance with their properties .for example, the previously determined atomic mass of beryllium ,14.09 ,was changed to the correct value 9.4, and beryllium was placed before Boron .

2)Mendeleev had kept some vacant places in the periodic table for elements that were yet to be discovered .three of these unknown elements were given the names of eka Boron , eka aluminium and Eka Silicon from the known neighbours and their atomic masses what indicates as 44,68 and 72 respectively .their properties were also predicted .later on these elements were discovered subsequently and were named as scandian (SC)gallium (Ga)and Germanium (Ge)respectively .