The basic difference between Mendeleev’s Periodic Law (A) and Modern Periodic Law (B) is:

 1 A is based on atomic weights while B is based on atomic numbers. 2 B is based on atomic weights while A is based on atomic numbers. 3 A is based on the number of isotopes while B is based on atomic numbers. 4 A is based on physical properties while B is based on chemical properties.

Subtopic: Â  Evolution of Periodic Table |
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The formula for the oxide formed by Eka-aluminum is:

1. ${\mathrm{EO}}_{4}$

2. ${\mathrm{E}}_{2}{\mathrm{O}}_{3}$

3. ${\mathrm{E}}_{3}{\mathrm{O}}_{2}$

4. EO

Subtopic: Â  Evolution of Periodic Table |
Â 86%
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The basic theme of the periodic table is:

 1 To classify the elements in a period according to their properties. 2 To classify the elements in a group according to their ionization enthalpy. 3 To classify the elements in periods and groups according to their properties. 4 To classify the elements in periods and groups according to their lustre.

Subtopic: Â  Evolution of Periodic Table |
Â 87%
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Those in a group that falls under the law of triads include:

1. Cl, Br, I

2. C, N, O

3. Na, K, Rb

4. H, O, N

Subtopic: Â  Evolution of Periodic Table |
Â 63%
From NCERT
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