what are the limitations of mendeleevs periodic table

Hi Snoby.. !!!!

Limitations are :

Position of hydrogen : Hydrogen is placed in Group IA. However, it actually resembles the elements of Group-IA (alkali metals ) as well as the elements of Group VII-A (halogens ). Thus, the position of hydrogen in the periodic table is not clear.

Position of isotopes : On the basis of atomic weight , various isotopes of the same elements should be assigned different places in the periodic table. Mendeleev could not provide separate places for isotopes.

Position of lanthanides and actinides : Fourteen elements following Lanthanum(known as lanthanides or rare earths) and the fourteen elements following Actinium (known as actinides or transuranic elements ) have not been provided separate and proper places in the Mendellev's table, rather they have been placed in two rows at the bottom of the table.

Disimilar elements placed together : Noble metals like Cu, Ag and Au are placed along with chemically dissimilar alkali metals in Group I . Similarly, Mn possessing very few similarities with halogens have been placed in VII group.

Similar elements separated : In Mendeleev's periodic table, certain chemically similar elements such as copper and mercury ; gold and platinum have been placed in different groups.

Anomalous pairs : In the Mendeleev's Table based on atomic weight, the positions of certain pairs , e.g. Argon( at. wt = 39.94) and potassium ( at. wt = 39.1) : Cobalt( at wt =58.93 ) and nickel ( at wt = 58.71 ) ; Tellurium at wt = 127.60) and iodine (atomic weight = 126.90 ) would be reversed. In other words, certain pairs of elements are misfit in the periodic table, if atomic weight is the basis of classification.

Hope this helps !!!!!!

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 position of lanthanide tell  ma about this

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haan

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Refer 10th Science Text book Page No.84. - LIMITATIONS OF MENDELEEV' S CLASSIFICATIONS

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Limitations of Mendeleevs periodic table:

  • The position of hydrogen is not justified in Mendeleevs periodic table. He positioned it in the first column above alkali metals. He did so because hydrogen and alkali metals have similar electronic configurations. Also, hydrogen reacts with halogens, oxygen and sulphur to form compounds whose formulae are similar to those of alkali metals.

Table: Hydrogen and alkali metals reacting with halogens

However, like halogens, hydrogen too is a gas and exists as a diatomic molecule (H2). It forms covalent compounds like halogens, and unlike alkali metals. Hence, it can also be placed above the halogen group.

Hence, we can say that hydrogen resembles alkali metals as well as halogens, and can be placed above either of them. This means that hydrogen cannot have a fixed position in the periodic table. Therefore, it is a limitation of Mendeleevs periodic table that hydrogen is not assigned a correct position in it.

  • The discovery of isotopes revealed another limitation of Mendeleevs periodic table. Atoms of the same elements having different number of neutrons are called isotopes. Isotopes have the same number of protons and electrons, but different number of neutrons. For example, the isotopes of chlorine are Cl-35 and Cl-37. They have the same chemical properties, but different atomic masses. Since Mendeleevs periodic table is based on the atomic masses of elements, isotopes have to be placed in different columns despite the fact that they represent the same element.

  • In Mendeleevs periodic table, atomic masses do not increase in a regular manner. As a result, it is not possible to predict the number of elements that might be present between two elements.

  • Although Mendeleev arranged the elements in the increasing order of their atomic masses, there are instances where he has placed an element with a slightly higher atomic mass before an element with a slightly lower atomic mass. For example, cobalt (whose atomic mass is 58.9) is placed before nickel (whose atomic mass is 58.7). This reversal was done to maintain a consistency in the properties of the elements present in a column, i.e., to group the elements with similar properties together.

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1 Position of isotopes
2 Position of Hydrogen
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1) The position of Hydrogen is still isn't fixed
2) the position of isotopes is not shown 
3)He used the basis of placeing as atomic masses  (from lower to higher)due to which some elements with higher atomic mass  are placed before followed by elements with lower atomic masses

 
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the position of hydrogen was not correctly defined.it was placed in group 1 although it resembles both the group 1 element.the alkali metals and the group 7 elements the halogens in thier properties.
in some cases mendeleev placed some elements according to thier similarties properties not by thier increasing order of thier atomic masses.thus the position of these elements was not justified.
isotopes were not given separate places in the peroidic table.
some similar elements were group separately while some dissimilar elements were grouped together.
mendeleev could not explain the cause of peroidicity in the elements.
the position of lathenide and actinide were not included in this table.
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the position of hydrogen was not correctly defined.it was placed in group 1 although it resembles both the group 1 element.the alkali metals and the group 7 elements the halogens in thier properties.
in some cases mendeleev placed some elements according to thier similarties properties not by thier increasing order of thier atomic masses.thus the position of these elements was not justified.
isotopes were not given separate places in the peroidic table.
some similar elements were group separately while some dissimilar elements were grouped together.
mendeleev could not explain the cause of peroidicity in the elements.
the position of lathenide and actinide were not included in this table.
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1 Position of hydrogen 2 Anomalous pair of element 3 Dissimilar elements placed together 4 Some similar element are separated 5 Position of Isotope
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Limitations are
1. Position of hydrogrn was not defined
2. Position of lanthinides and anthanides is not defined
3. Position of transation triades
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position of hydrogen and isotopes are not defined .
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refer to ncert
 
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it will help u
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The position of isotopes. Position of hydrogen. Positionof Ni & Co.
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The limitations of mendeleev are as follows:
  • he cannot tell the position of hydrogen
  • he cannot tell the position of isotopes
  • he cannot tell the position of anomalous pairs.
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Limitations of Mandeleev’s periodic table : Inspite of many advantages, the Mendeleev’s periodic table has certain defects also. Some of these are given below ;

(A) Position of hydrogen : Position of hydrogen in the periodic table is uncertain. It has been placed in 1A group with alkali metals, but certain properties of hydrogen resemble those of halogens. So, it may be placed in the group for halogens as well.

(B) Position of isotopes : Isotopes are the atoms of the same element having different atomic masses. Therefore, according to Mendeleev’s classification these should be placed at different places depending upon their atomic masses. For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.

(C) Anomalous pairs of elements “ In certain pair of elements, the increasing order of atomic masses was not obeyed. In these, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses.

 For example :

– The atomic mass of argon is 39.9 and that of potassium 39.1 But argon is placed before potassium in the periodic table.

– Tellurium (at. mass = 127.6 ) is placed before iodine (at. mass = 126.9)

(D) Some similar elements are separated, in the periodic table. For example copper (Cu) and mercury (Hg), barium (Ba) and lead (Pb). On the other hand some dissimilar elements have been placed together in the same group.

(E) Cause of periodicity : Mendeleev could not explain the cause of periodicity among the elements.

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thanks thats nice information.
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1.could not explain isotopes of elements
2.could not explain the increasing atomic mass
3.could not assign proper position of hydrogen in its table
 
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bosudike
 
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I have my ans in my text book come to my home i will tell u
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was unable to determine the position of hydrogen and position of isotopes 
 
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there is no fixed position of hydrogen.
dissimilar elements are placed together 
 
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Hydrogen is placed in Group IA. However, it actually resembles the elements of Group-IA (alkali metals ) as well as the elements of Group VII-A (halogens ). Thus, the position of hydrogen in the periodic table is not clear.

Position of isotopes : On the basis of atomic weight , various isotopes of the same elements should be assigned different places in the periodic table. Mendeleev could not provide separate places for isotopes.

Position of lanthanides and actinides : Fourteen elements following Lanthanum(known as lanthanides or rare earths) and the fourteen elements following Actinium (known as actinides or transuranic elements ) have not been provided separate and proper places in the Mendellev's table, rather they have been placed in two rows at the bottom of the table.

Disimilar elements placed together : Noble metals like Cu, Ag and Au are placed along with chemically dissimilar alkali metals in Group I . Similarly, Mn possessing very few similarities with halogens have been placed in VII group.

Similar elements separated : In Mendeleev's periodic table, certain chemically similar elements such as copper and mercury ; gold and platinum have been placed in different groups.

Anomalous pairs : In the Mendeleev's Table based on atomic weight, the positions of certain pairs , e.g. Argon( at. wt = 39.94) and potassium ( at. wt = 39.1) : Cobalt( at wt =58.93 ) and nickel ( at wt = 58.71 ) ; Tellurium at wt = 127.60) and iodine (atomic weight = 126.90 ) would be reversed. In other words, certain pairs of elements are misfit in the periodic table, if atomic weight is the basis of classification.
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Inspite of many advantages, the Mendeleev?s periodic table has certain defects also. Some of these are given below ;

(A) Position of hydrogen : Position of hydrogen in the periodic table is uncertain. It has been placed in 1A group with alkali metals, but certain properties of hydrogen resemble those of halogens. So, it may be placed in the group for halogens as well.

(B) Position of isotopes : Isotopes are the atoms of the same element having different atomic masses. Therefore, according to Mendeleev?s classification these should be placed at different places depending upon their atomic masses. For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.

(C) Anomalous pairs of elements ? In certain pair of elements, the increasing order of atomic masses was not obeyed. In these, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses.
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When the substances is containing oils and fats it exposed to air they get oxidised and become raincid due to which their smell , taste and colour changed , so this process is called raincidity
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Ethyl alcohol on heating with. Conc H2SO4 gives ?
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He cannot tell the position of hydrogen He cannot tell the position of isotopes He cannot tell the position of anomalous pairs
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Thanku So much every body nice and easy answers
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no
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following are the defects:
  • Position of hydrogen still dicey. It is not fixed till now.
  • Position of Lanthanides and actinides has not been given inside the main body of periodic table.
  • It does not reflect the exact distribution of electrons of some of transition and inner transition elements.
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hey
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Fucky
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Limitations
1.No fixed position of hydrogen
2.No place for isotopes
3.Increasing order of atomic mass could not be maintained
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position of H:
in mendeleevs periodic table the position of H is unsatisfactory. he did not give a plausible explanation and did not place H along with alkali elements nor the halogens.

position of isotopes:
isotopes of an element have similar chemical properties but different masses. thus according to mendeleevs periodic table isotopes should be placed at different positions based on their atomic masses but it was not so.

similar elements were not placed together:
Cu in group 1B and Hg in group 2B. they show similar properties but they were placed in different groups.

anomalous pair of elements:
in mendeleevs periodic table there are a number of anomalous pair of elements where the elements having lower atomic mass has been placed before the element having higher atomic mass.
 
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1 position of hydrogen
2 position of isotops- Mendeleev's periodic table is based on atomic masses hence isotops are biggest enomly with respect to their position.
3 enormous position of some pairs of elements.
4 no resemblenss of elements with in sub groups.
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Limitations of mendeleev periodic table are as follows:
* The position of hydrogen was not justified or hydrogen was not given a correct position.
* Isotopes of elements posed a challenge because of the different atomic masses.
* Atomis masses did not increase in a regular manner since nickel and cobalt were arranged in the same group.
(Nickel has atomic mass 28 but cobalt has atomis mass 27)
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•No place for isotopes •No fixed position for hydrogen
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no fixed position for hydrogen, no place for isotope.
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Limitations of mendeleeves periodic table: I)no fixed and correct position was assigned to hydrogen in mendeleeves periodic table. II)Isotopes which were discovered later did not find a place in mendeleeves periodic table.III)Atomic masses, which is the basis of classification do not increase in aregular manner when we go from one element to the next . Therefore it was not possible to predict how many elements could be discovered between the two elements.IV)The position of an element in the periodic table tells us about the chemical reactivity of the element.
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Hope this may help u

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1. It has made the study of element simpler and easy.

2.It is based upon more fundamental property of an element i.e. atomic number.

3.It helped in the correction of wrong atomic number.

4.Some gaps were left in the periodic table for undiscovered elements, but predicted the properties of these element.
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There are many limitation of the mendeleevs periodic table.

Hydrogen: he did not give a proper place for hydrogen. It resembles with alkali metals as well as halogens.

Isotopes :the atomic mass of isotopes is different but mendeleeves could not give place for isotops.

Inversion of periodic table: he arranged elements in increasing atomic mass but he place cobalt before nikle .
Noble gas :in his periodic table there is no place for noble gases.
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Achievements of the Mendeleev's periodic tables are as under:-

1) Systematic study of elements:-

?As the elements having same properties are grouped together so it becomes very useful to remember the properties of large number of elements in a systematic way.

2) ?Prediction of new elements:-

?Mendeleev predicted the properties of those missing elements from the known properties of the other elements in the same group. On the basis of this, he named Gallium as Eka-Almunium, Germanium as Eka-Silicon and Scandium as Eka-Boron.

3) Correction of atomic mass:-

?Atomic mass of beryllium was corrected from 13.5 to 9. Atomic mass of indium, gold and platinum were also corrected.
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Hi
1.Mandeleev's table was in increasing order of mass no ,so isotopes became a limitation.
2.Position of Hydrogen
3.unmatched groups like ,Au and Cu placed with alkali metals
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He could classify all the 63 elements known at that time on the basis of similarities in properties.

2. He left gaps for the elements yet to be discovered.

3. He predicted the properties of those yet to be discovered elements and thus, helped in the discovery of other elements later on.

4. He named these elements by prefixing a sanskrit numeral 'Eka' (one), 'Divi' (two), 'Tri' (three), etc.to the names of the preceding preceding similar element in the same group. For example : eka - boron, eka - aluminium, eka - silicon, divi - manganese, eka - tantulum, etc.

All these elements were discovered later and did have the properties similar to those predicted by mendeleev. For example -

PROPERTIES EKA - ALUMINIUM GALLIUM

Atomic mass 68 69.7

Formula of oxide E2O3 Ga2O3

Formula of chloride ECL3 GaCl3

Demerits -

1. Although most of the elements were placed in the order of increasing atomic weights but this increasing order could not be maintained in all cases. For example - Cobalt atomic mass is 58.93u preceded Nickel 58.71u preceded Tellurium 127.6 preceded Iodine 126.90, thus he couldnt maintain similarities in properties.

2. Mendeleev periodic table did not provide space for noble gases which were discovered later.

3. Moreover there was no space left for isotopes in medeleev's periodic table.
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Here is ur answer

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Please find this answer

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Is salt a homogeneous or heterogeneous mixture
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There is no fixed position for hydrogen. Second one is position of isotopes couldn't be explained and the third one is wrong order of atomic masses of some elements couldn't be explained
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Neet ki class kitne time Lagti Hai
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limitation of mendeelev's periodic table
 
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Please find this answer

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Please find this answer

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Please find this answer

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1) No position allotted to hydrogen.
2) Isotopes position was not defined.
3) The atomic masses does not increase in a regular manner. Therefore very difficult to predict how many elements could be discovered between two elements.
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