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प्रश्न
What are the demerits of Mendeleev’s periodic table?
Write the demerits of Mendeleev's periodic table.
उत्तर
Demerits of Mendeleev’s periodic table:
1. The whole number atomic mass of the elements cobalt (Co) and nickel (Ni) is the same. Therefore there was ambiguity regarding their sequence in Mendeleev’s periodic table.
2. Isotopes were discovered a long time after Mendeleev put forth the periodic table. As isotopes have the same chemical properties but different atomic masses, a challenge was posed in placing them in Mendeleev’s periodic table.
3. When elements are arranged in increasing order of atomic masses, the rise in atomic mass does not appear to be uniform. It was not possible, therefore, to predict how many elements could be discovered between two heavy elements.
4. Position of hydrogen: Hydrogen shows similarity with halogens (group VII). For example, the molecular formula of hydrogen is H2 while the molecular formulae of fluorine and chlorine are F2 and Cl2, respectively. In the same way, there is a similarity in the chemical properties of hydrogen and alkali metals (group I). There is a similarity in the molecular formulae of the compounds of hydrogen alkali metals (Na, K, etc.) formed with chlorine and oxygen. On considering the above properties it can not be decided whether the correct position of hydrogen is in the group of alkali metals (group I) or in the group of halogens (group VII).
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संबंधित प्रश्न
Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, Al, Si, Ba.
Name three elements that have a single electron in their outermost shells.
Name two elements that have two electrons in their outermost shells.
Name three elements with filled outermost shells.
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
On what basis did mandeleev arrange the elements in his periodic table?
State Mendeleev's periodic law.
(a) Write its electronic configuration and determine its valency.
(b) Is it more reactive or less reactive than Ca (atomic number 20)? Justify your answer giving reason.
(c) Is it a metal or a non-metal?
(d) Write the formula of its oxide.
Explain in brief how Mendel interpreted his results to show that the traits may be dominant or recessive.
Use Mendeleev's Periodic Table to predict the formula of hydrides of carbon and silicon.
Which group of elements was missing from Mendeleev's original periodic table?
Name two elements whose atomic weights were corrected on the basis of their positions in Mendeleev's periodic table.
How many elements were known at the time of Mendeleev's classification of elements?
What was the basis of Mendeleev's classification?
State the contributions made by Mendeleev towards the periodic table.
According to Mendeleev’s periodic law, properties of elements are periodic function of their _______.
In Mendeleev’s periodic table eka- silicon was later named as _______.
Write the molecular formula of the oxide of any one of the elements in Mendeleev’s periodic table.
According to Mendeleev’s periodic law properties of elements are ______.
While designing the periodic table, Mendeleev considered the chemical and physical properties of the elements.
Write scientific reason.
Mendeleev kept vacant places in the periodic table.
Write scientific reason.
There was no definitive place for isotope in Mendeleev’s periodic table.
On which basis Mendeleev organised periodic law?
What challenges did Mendeleev face in following periodic law?
In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the Periodic Table later?
The properties of eka-aluminum predicted by Mendeleev are the same as the properties of a later discovered elements: ______
An element has 12 protons. The group and period to which this element belongs is ______
Which of the following oxide is most basic?
The total number of electrons present in the first twenty elements of the periodic table is ______
In Mendeléev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later
Which of the following statement (s) about the Modern Periodic Table are incorrect
- The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number
- The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses
- Isotopes are placed in adjoining group (s) in the Periodic Table
- The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number
Give an account of the process adopted by Mendeléev for the classification of elements. How did he arrive at “Periodic Law”?
State Mendeleev’s Law of Periodicity.
