Chemistry Class-11: Chapter – 3. Classification of Elements and Periodicity in Properties-Part – 6 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Question: 28

Among the elements B, Al, C and Si,

(i) Which element has the highest first ionization enthalpy?

(ii) Which element has the most metallic character? Justify your answer in each case.


(i) Carbon

(ii) Aluminium


Write four characteristic properties of p-block elements.


Question: 30

Choose the correct order of atomic radii of fluorine and neon (in pm) out of the options given below and justify your answer.





Answer: (i)

Question: 31

Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.

Question: 32

Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionization enthalpy than nitrogen. Explain.


The outermost electronic configuration of nitrogen is very stable because p-orbital is half filled. Addition of extra electron to any of the 2p orbital requires energy.

Oxygen has electrons in orbitals and acquires stable configuration i.e.. , configuration after removing one electron.

Question: 33

First member of each group of representative elements (i.e.. , s and p-block elements) shows anomalous behavior. Illustrate with two examples.

Question: 34

p-Block elements form acidic, basic and amphoteric oxides. Explain each property by giving two examples and also write the reactions of these oxides with water.

Question: 35

How would you explain the fact that first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?


After removing 1 electron from the sodium atom the ion formed acquires the configuration of inert gas, neon. The second electron is removed from one of the 2p-orbitals which are completely filled i.e.. , have a total of 6 electrons and are closer to the nucleus.

Question: 36

What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.

Question: 37

Arrange the elements N, P, O and S in the order of-

(i) increasing first ionization enthalpy.

(ii) increasing non-metallic character.

Give reason for the arrangement assigned.




Question: 38

Explain the deviation in ionization enthalpy of some elements from the general trend by using Fig. 3.2.

Ionization Enthalpy

Question: 39

Explain the following:

(a) Electronegativity of elements increase on moving from left to right in the periodic table.

(b) Ionization enthalpy decrease in a group from top to bottom?


(a) Decrease in size of atom and increase in nuclear charge.

(b) Increase in atomic size.