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Ayushman

Feb 26, 2014

write the advantages and disadvantages of mendeleev's periodic table and modern periodic table with examples.

write the similarities between dobereiner's triads and newland's law of octaves?

write the change in modern periodic table as we go from left to right and top to bottom in context to -

(1)valency electrons

(2)valency

(3)electronegativity 

(4)metallic character

(5)electron affinity

(6)atomic size

also explain how?

Answers(8)

Answer

Rohit Jha

Advantage of Mendeleev Periodic Table :-
1.He left blank  Places which help scientist to discover new element
2.When Noble gasses was discovered Hel could add  it to periodic table without any major changle 
3.He predicted the property of new element 

Disadvantages :-
1. Couldn't explain position of Hydrogen 
2.Couldn't answer the question "Can we have an element with atomic mass 3 between Hydrogen and Helium 
3 He placed cobalt before Nickel though Cobalt has more mass

Shubh Gupta

Well you can watch this video to clearly understand the concept with a simple demonstration. I really find it very helpful. Plus you dont have to read long answer. Just watch this interactive video... http://bit.ly/1vS6ORx
Please give your feedback for the answer.

Rohit Jha

Some Doberenier trait also exist in Newland law of octave 
Like
Li
Na
K

Agam Gupta

Advantage of Mendeleev Periodic Table :-
1.He left blank  Places which help scientist to discover new element
2.When Noble gasses was discovered Hel could add  it to periodic table without any major changle 
3.He predicted the property of new element 

Disadvantages :-
1. Couldn't explain position of Hydrogen 
2.Couldn't answer the question "Can we have an element with atomic mass 3 between Hydrogen and Helium 
3 He placed cobalt before Nickel though Cobalt has more mass

Priyanshu

Uses:
�i) � Atomic weights of elements were determined with the help of periodic table
Atomic weight = Valency ´ Equivalent weight = Group number ´ Equivalent weight.
�ii) Atomic weight of elements were corrected. Atomic weight of Be was calculated to be�
3 ´ 4.5 = 13.5 by considering its valency 3. Mendeleef calculated it 2 ´ 4.5 = 9.
�iii)� Discovery of new elements – In Mendeleef's periodic table two consecutive members differ by two or three units in the atomic weight. Where this gap was more, the gaps were left in the periodic table.

Defects:
i)��� Position of hydrogen is uncertain. It has been placed in IA and VIIA groups because of its resemblance with both the groups.
ii) � No separate positions were given to isotopes.
iii)�� It is not clear whether the lanthanides and actinides are related to IIA or IIIB group.
iv) Although there is no resemblance except valency of subgroups A and B, they have been put in the same group.
v) � Order of increasing atomic weights is not strictly followed in the arrangement of elements in the periodic table. For e.g. – Co (At.wt. 58.9) is placed before I (127) and Ar (39.9) before K (39).

Dinesh Singha

mendeleev's periodic table 
adv                                                                               disadv
-- elements in groups showed                           -- couldn't explain position of hydrogen
    similar chemeical properties                         --elements weren't placed according to increasing
 -- vacant spaces for undiscovered                                    atomic mass
   elements                                                        -- no satisfactory position of isotopes
  • dobereiner's triads also existed in newland's octaves
  • eg :- lithium, sodium,potassium                                                                           
            left to right                                                                         top to bottom
  1.  increases                                                                          remains same
  2. first increases from 1 to 4 thendecreases from 3 to 0             remains same
  3. increases                                                                           decreases
  4. decreases                                                                             increases
  5. i don't know
  6. decreases                                                                             increases

Rohit Jha

In Periods 
3. Valency increases when we go left to right till group 14 then decreases 
    Electronegativity increases when we go left to right 
    Metallic Character decreases when we go left to right 
    Atomic size decreases when we go left to right 

Greeny joby

mendeleev's periodic table 
adv                                                                               disadv
-- elements in groups showed                           -- couldn't explain position of hydrogen
    similar chemeical properties                         --elements weren't placed according to increasing
 -- vacant spaces for undiscovered                                    atomic mass
   elements                                                        -- no satisfactory position of isotopes
  • dobereiner's triads also existed in newland's octaves
  • eg :- lithium, sodium,potassium                                                                           
            left to right                                                                         top to bottom
  1.  increases                                                                          remains same
  2. first increases from 1 to 4 thendecreases from 3 to 0             remains same
  3. increases                                                                           decreases
  4. decreases                                                                             increases
  5. i don't know
  6. decreases                                                                             increases
  
















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