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Mendeleev left gaps in his periodic table for undiscovered elements. Which of the following properties was NOT used by him to predict the properties of these missing elements?
Atomic weight
Density
Formulae of oxides and hydrides
Radioactive decay 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
Which of the following pairs of elements would have been placed in the SAME group in Mendeleev's periodic table but DIFFERENT groups in the modern periodic table?
Tellurium (Te) and Iodine (I)
Sodium (Na) and Potassium (K)
Calcium (Ca) and Magnesium (Mg)
Iron (Fe) and Cobalt (Co)
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
If Mendeleev had known about the concept of isotopes, how would his periodic table have been different?
Isotopes of the same element would have been placed in different groups
Isotopes of the same element would have occupied the same position
The table would have been organized based on neutron number
The concept of periodicity would have been discarded
Mendeleev predicted the existence of an element he called eka-aluminum. Which of the following properties was NOT a prediction Mendeleev made about eka-aluminum?
The atomic weight of the element
The density of the element
The melting point of the element
The existence of several isotopes of the element
Element 'X' has the following properties: it exhibits variable oxidation states, forms coloured compounds, and its highest oxidation state corresponds to its group number. 'X' is most likely situated in which block of the periodic table?
s-block
p-block
d-block
f-block
Mendeleev left gaps in his periodic table. Which of the following elements was predicted by Mendeleev and later discovered, fitting into one of these gaps?
Sodium
Potassium
Calcium
Gallium
Mendeleev arranged elements in increasing order of their:
Atomic number
Atomic weight
Number of neutrons
Number of valence electrons
Which of the following properties did Mendeleev primarily use to predict the properties of undiscovered elements?
Number of valence electrons
Atomic number
Properties of elements surrounding the gap
Radioactivity
