Chemistry Class-11: Chapter –3. Classification of Elements and Periodicity in Properties-Part 2

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Question: 9

The elements in which electrons are progressively filled in 4f-orbital are called

(i) Actinoids

(ii) Transition elements

(iii) Lanthanoids

(iv) Halogens

Answer: (iii)

Question: 10

Which of the following is the correct order of size of the given species:





Answer: (iv)

Question: 11

The formation of the oxide ion, , from oxygen atom requires first an exothermic and then an endothermic step as shown below:

Thus process of formation of O2– in gas phase is unfavorable even though is isoelectronic with neon. It is due to the fact that,

(i) Oxygen is more electronegative.

(ii) Addition of electron in oxygen results in larger size of the ion.

(iii) Electron repulsion outweighs the stability gained by achieving noble gas configuration.

(iv) ion has comparatively smaller size than oxygen atom.

Answer: (iii)

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