Assertion: Mendeleev arranged the elements in increasing order of their atomic masses and according to their chemical properties. Reason: Mendeleev even predicted the existence of some yet to be discovered elements on the basisi of gaps in his periodic table.
Answers
ANS:
>YES HE LEAVES GAPS FOR ELEMENTS WHICH IS TO BE DISCOVERED HE BEFORE ITSELF FOUND EKA SILICA AND EKA ALUMINIUM THIS MEANS NOW FOUNDED GALLIUM AND GERMANIUM LOOK LIKE SAME PROPERTIES OF THE EKA SILICA AND EKA ALUMINIUM.
Mendeleev's Periodic classification
Explanation:
Mendeleev classification
Periodic table is chart of elements prepared in such a way that elements having similar properties occur in same vertical group.
According To Mendeleev periodic law: -
- Properties of elements are periodic function of their atomic in this there are seven periods and eight groups. Out of 8 groups seven are of normal elements and one of transition elements.
- “He also left gaps in his table for unknown elements”
- He thought that when these elements would be discovered later,then they can be placed in table without disturbing other elements.
MERITS
He grouped the elements on the basis of atomic mass.
He left gaps for undiscovered elements like Gallium, Scandium germanium. Even he left full group vacant for undiscovered inert gases.
He could predict proportions of several elements on basis of their position in periodic table like Ga, Sc etc.
He could predict errors in atomic weights of some elements like gold, platinum etc.
ANOMALIES.
1. Position of isotopes could not be explained.
2. wrong order of atomic masses could not be explained for example: - as Argon atomic mass 40 come first and K with low atomic mass) 30) should come later but k should be placed first all to his low.
3. Position of hydrogen could not be explained.
4. Some dissimilar elements are grouped together while some elements are placed in different groups.
The above assertion and reason is correct but to a assertion the reason is not justified .
He arranged the elements according to increasing because of periodicity in properties that he could see in the elements .