Periodic Classification of Elements class 10 science NCERT In Text solution

Periodic Classification

NCERT In Text Questions

What were the limitations of Döbereiner’s classification?

Answer: Limitations of Dobereiner’s classification:


Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.

Answer: Yes, Dobereiner’s triads exist in the columns of Newland’s Octaves.

Example: In the Dobereiner’s triads Lithium, Sodium and Potassium make a triad, and these elements also present in the same column of Newland’s Octaves as these have same properties.

What were the limitations of Newlands’ Law of Octaves?

Answer: Limitations of Newland’s Law of Octaves:

Use Mendeléev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, AI, Si, Ba.

Answer:


Besides gallium, which other elements have since been discovered that were left by Mendeléev in his Periodic Table? (any two)

Answer: Scandium and Germanium

What were the criteria used by Mendeléev in creating his Periodic Table?

Answer: Mendeleev used atomic mass of the elements as the unique criteria of the elements. He proposed that the chemical properties of elements are the periodic function of their atomic masses. And thus, he arranged the elements in the increasing order of their atomic masses.

Why do you think the noble gases are placed in a separate group?

Answer: Since, noble gases are inert and all of them show similar properties, thus they have unique properties compare to other elements, thus they are placed in a separate group in Periodic Table.

How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?

Answer: Various anomalies of Mendeleev’s Periodic Table removed as follows in the Modern Periodic Table:

Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?

Answer: Beryllium and Calcium. These elements show chemical reactions similar to magnesium because magnesium, calcium and beryllium belong to same group, i.e. Group 2nd in the Modern Periodic Table.

Name

  1. Three elements that have a single electron in their outermost shells.

    Answer: Hydrogen, Lithium and Sodium
  2. Two elements that have two electrons in their outermost shells.

    Answer: Calcium and Magnesium
  3. Three elements with filled outermost shells.

    Answer: Neon, Argon and Krypton

Explain the following:

Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

Answer: Lithium, Sodium and Potassium have following similarities:

Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?

Answer: Following properties are common in the atoms of Helium and Neon:

In the Modern Periodic Table, which are the metals among the first ten elements?

Answer: Lithium and Beryllium

By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic? Ga Ge As Se Be

Answer:By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristic? Ga Ge As Se Be



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