Unit-4 Periodic Table and Periodicity of Properties
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Unit-4 Periodic Table and Periodicity of Properties
Answer: Dobereiner grouped elements into triads of similar chemical properties.
Answer: The middle element's atomic mass is near the average of the other two.
Answer: The fourth period starts with potassium, atomic number 19.
Answer: Dobereiner's triads consisted of sets of three elements.
Answer: Newlands' law did not apply to elements heavier than calcium.
Answer: 4s fills before 3d, which fills before 4p, following energy order.
Answer: Newlands arranged elements by increasing atomic mass.
Answer: Mendeleev's periodic law used atomic mass as its basis.
Answer: Greater nuclear charge and smaller radius make Mg's electron harder to remove.
Answer: Every eighth element resembled the first, like notes in a musical octave.
Answer: The modern table arranges elements by increasing atomic number.
Answer: Higher effective nuclear charge pulls the same-shell electrons inward.
Answer: Mendeleev used increasing atomic mass as the basis of his table.
Answer: Elements are classified into blocks by the last filled subshell.
Answer: Germanium matched Mendeleev's predicted eka-silicon.
Answer: He predicted the existence and properties of undiscovered elements.
Answer: Helium has a full outermost shell, so it behaves like a noble gas.
Answer: Gallium's properties matched the predicted eka-aluminium.
Answer: Moseley discovered that atomic number determines element properties.
Answer: Like alkali metals, hydrogen has one valence electron.