Question

Three limitations of mendeleev periodic table which was taken care in modern periodic table

Answer 1

$\bold{MENDELEEF'S \: PERIODIC \: TABLE}$

Mendeleef arranged elements in increasing order of atomic weight in form of a table called periodic table.

▶He had put forward the concept of peroidicy of peroperties in modern periodic table at regular interval of time.

▶Elements were arranged in vertical groups and horizontal peroids.

▶Elements in same group had the same valency.

▶Number of gaps were left for undiscovered elements.

▶Property of undiscovered element were predicted.

$\bold{ITS \: DEFECTS}$

Mendeleef's periodic table had three defects which were taken in consider while making modern periodic table.

▶$\bold{Anamolus \: Pair \: Of \: Element }$

Some elements who were having higher atomic weight have been given position before element having lower atomic weight.

This problem was sorted out by arranging elements according to their atomic weight.

▶$\bold{Position \: Of \: Rare \: Earth \: And \: Actinides}$

It was justified when elements were arranged according to atomic number.

▶$\bold{Position \: Of \: Isotopes}$

Isotopes were misplaced which was also sorted out when elements were arranged according to atomic number in modern periodic table.

Answer 2

$\boxed{\textbf{Mendeleev 's Periodic Table}}$

$\bold{\implies}$In 1869 Russian chemist Mendeleev construct his Periodic Table with then known total 63 elements in 8 vertical Columns(groups) and 6 horizontal rows(periods).

$\underline{MERITS}$

$\implies$Mendeleev leave some box in his Periodic table for some unknown elements based on a particular properties of particular group.

He named also Some of Unknown Metals like Eka Boron now known as scandium in his Periodic Table.

$\implies$Mendeleev corrected the doubtful atomic weight of some elements like indium .Which was 76 then based on indium oxide had formula InO he corrected the formula as $InO_2O_3$ and find Atomic Weight of Indium as 113.

$\underline{DEMERITS}$

Anomalous Pairs$\implies$In Mendeleev Periodic Table some Elements which have higher atomic Weights placed Before lower atomic weight just because similarity Between them In Chemical Properties.

Like=Cobalt 58.9 placed Before Nickel 58.6

Position of Hydrogen$\implies$Not Specific Position of Hydrogen in Table.

Positions of Isotopes$\implies$No position of Isotopes of a element in Table.

Isotopes Termed as Different atomic weight of A same Elements.

Position of lanthanides and actinides$\implies$Lanthanum and Actinium have not been provided seperate spaces places in Periodic Table.