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प्रश्न
What challenges did Mendeleev face in following periodic law?
उत्तर
The challenges faced by Mendeleev while following periodic law were:
- Mendeleev had to arrange the elements with the thought that the information available till then was not final but it could change.
- He had to revise the atomic masses of some elements so as to give them a proper place in the periodic table in accordance with their properties. For example, the previously determined atomic mass of beryllium, 14.09, was changed to the correct value 9.4, and beryllium was placed before boron.
- He had to keep some vacant places in the periodic table for elements not discovered till then. However, he predicted the atomic masses and properties of some these unknown elements.
- There was no place reserved for noble gases in Mendeleev’s original periodic table. So, when noble gases were discovered, he had to include them. He did this without disturbing the original periodic table by creating ‘zero’ group.
- He had to indicate a question mark before the symbol of the element due to uncertainty in the names of some of the elements.
- There was ambiguity regarding the sequence of elements having a whole number atomic mass such as Co and Ni.
- It was difficult to place isotopes of elements as they have the same chemical properties but different atomic masses.
- It was not possible to predict how many elements could be discovered between two heavy elements as the rise in atomic mass is not uniform. In addition to this, it was difficult to decide the position of hydrogen in the periodic table.
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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.
Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic?
State any three demerits of Mendeleev’s periodic table.
On what basis elements are arranged in periodi table now?
What were the two criteria used by Mendeleev to classify the elements in his periodic table?
State Mendeleev's periodic law.
Write a short note.
Mendeleev’s periodic law.
Write the merits of Mendeleev’s periodic table.
Use Mendeleev's Periodic Table to predict the formula of oxides of potassium, aluminum, and barium.
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.
Answer the following question:
Name two elements having a single electron in their outermost shell.
What are the demerits of Mendeleev’s periodic table?
State the contributions made by Mendeleev towards the periodic table.
Beryllium : alkaline earth metal : : sodium: _______
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.
What are the limitations of Mendeleev's periodic table?
An element has 12 protons. The group and period to which this element belongs is ______
The total number of electrons present in the first twenty elements of the periodic table is ______
According to Mendeléev's Periodic Law, the elements were arranged in the periodic table in the order of
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
In Mendeléev’s Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.
Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeléev.
Properties of the elements are given below. Where would you locate the following elements in the periodic table?
- A soft metal stored under kerosene
- An element with variable (more than one) valency stored under water.
- An element which is tetravalent and forms the basis of organic chemistry
- An element which is an inert gas with atomic number 2
- An element whose thin oxide layer is used to make other elements corrosion resistant by the process of “ anodising”
Give an account of the process adopted by Mendeléev for the classification of elements. How did he arrive at “Periodic Law”?
Mendeleev's periodic table was based on ______.
