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NEET Questions / Chemistry / Classification of Elements and Periodicity in Properties
Mendeleev classified elements based on atomic weight, while the modern periodic table uses atomic number. Which anomaly in Mendeleev's table was directly resolved by this change?
Placement of noble gases
Position of tellurium and iodine
Existence of isotopes
Lanthanide contraction
In Mendeleev's periodic table, eka-silicon was predicted to have a density of 5.5 g/cm³. Germanium, later discovered to be eka-silicon, has a density of 5.323 g/cm³. This difference in predicted and observed density primarily highlights which limitation of Mendeleev's table?
Inability to predict the existence of noble gases
Placement of isotopes of the same element
Reliance on atomic weight as the primary organizing principle
Lack of understanding of the underlying electronic structure of atoms
Mendeleev arranged elements in increasing order of their:
Atomic number
Atomic weight
Number of neutrons
Number of valence electrons
Mendeleev placed some elements with higher atomic weights before elements with lower atomic weights. This was done to:
Follow alphabetical order
Account for undiscovered elements
Maintain the periodicity of chemical properties
Reflect the abundance of elements
Mendeleev arranged the elements in his periodic table based primarily on:
Atomic number
Number of neutrons
Atomic weight
Number of valence electrons
What was the primary basis for placing elements in the same period in Mendeleev's table?
Similar chemical properties
Increasing atomic number
Increasing atomic weight
Same number of valence electrons
Mendeleef’s Periodic Table is upset by the fact that
Many elements has several isotopes
Noble gases do not form compounds
Some groups stand divided into two sub groups A and B
Atomic weights of elements are not always whole numbers
Mendeleef’s Periodic Table is upset by the fact that
Arranging elements solely by increasing atomic weight leads to some elements being out of order in terms of their properties.
The discovery of noble gases completely disrupted the order of the periodic table.
Elements with similar atomic weights always have similar properties.
Mendeleev did not account for the existence of isotopes.
