Question

LIST ACHIEVEMENT'S OF MENDELEEVS CLASSIFICATION?(3 MARK)

PLZ ANSWER IN A CLARITY

Answer 1

Achievements of Mendeléev’s periodic table:

• element with a slightly greater atomic mass were placed

• before an element with a slightly lower atomic mass with an inverted sequence so as to group the elements with similar properties. For example, cobalt with atomic mass 58.9 was placed before nickel with atomic mass 58.7.

• He left some gaps in the Periodic Table with the prediction of

• existence of some elements that were not discovered at that time.

• He named the future elements by prefixing a Sanskrit numeral, Eka (one) to the name of preceding element in the same group.

• For instance, scandium, gallium and germanium, discovered later, have properties

•similar to Eka–boron, Eka–aluminium and Eka–silicon, respectively.

• Noble gases like helium (He), neon (Ne) and argon (Ar) were discovered

• later as they are present in exceptionally low concentrations in the atmosphere due to their inertness.

Answer 2

$\bold{ \underline{Mendeleev \: Periodic \: table:-}}$

=>The physical and chemical properties of elements are periodic function of their atomic mass .

$\bold{ \underline{Achievements :-}}$

➡In order to adjust elements in his periodic table the sequence was inverted in which elements with slightly greater atomic mass were placed before the element with Lower atomic mass.

for example:- Cobalt (Co) with atomic mass 58.93 and Nickel (Ni) with 58.71

➡He left some gaps from the Undiscovered periodic table . He predicted the existence of some element that had not been discovered.

➡He named them by prefixing Sanskrit numeral Eka(one) to the name of preceding element in the same group.

for example:- Scandium,Gallium, Germanium discovered later has properties to Eka- Boron( Scandium) , Eka - aluminium (Gallium) , Eka -silicon (Germanium)

➡ Noble gases which were discovered later could be placed in new group without disturbing the existing order.