Advertisements
Advertisements
Question
What challenges did Mendeleev face in following periodic law?
Solution
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.
APPEARS IN
RELATED QUESTIONS
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.
Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as
State any three demerits of Mendeleev’s periodic table.
State Mendeleev's periodic law.
What chemical properties of elements were used by Mendeleev in creating his periodic table?
List two contrasting visible characters of garden pea Mendel used for his experiment.
State Mendeleev's periodic law.
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?
Answer the following question:
Name two elements having a single electron in their outermost shell.
What are the demerits of Mendeleev’s periodic table?
What was the basis of Mendeleev's classification?
In Mendeleev’s periodic table eka- silicon was later named as _______.
Beryllium : alkaline earth metal : : sodium: _______
Write the molecular formula of the oxide of any one of the elements in Mendeleev’s periodic table.
Write scientific reason.
Mendeleev kept vacant places in the periodic table.
State Mendeleev’s Periodic Law.
On which basis Mendeleev organised 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?
Which of the following are the characteristics of isotopes of an element?
(i) Isotopes of an element have the same atomic masses
(ii) Isotopes of an element have the same atomic number
(iii) Isotopes of an element show the same physical properties
(iv) Isotopes of an element show the same chemical properties
Which of the following properties does not match the element of the halogen family?
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”
Which group of elements could be placed in Mendeléev's Periodic Table without disturbing the original order? Give reason.
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.
List the features of Mendeleev’s Periodic Table.
Mendeleev's periodic table was based on ______.
Name the elements whose compounds formed the basis of classification in Mendeleev's periodic table. Why did Mendeleev choose these elements?
How the formulae of these compounds had helped Mendeleev in deciding the position of an element in his periodic table?
