ncert file of chemistry chapter 3 class 11
Answers
Answer:
What is the basic theme of organisation in the periodic table?
2. Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
3. What is the basic difference in approach between the Mendeleev’s Periodic Law and the Modern Periodic Law?
4. On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
5. In terms of period and group where would you locate the element with Z =114?
6. Write the atomic number of the element present in the third period and seventeenth group of the periodic table.
7. Which element do you think would have been named by
(i) Lawrence Berkeley Laboratory
(ii) Seaborg’s group?
8. Why do elements in the same group have similar physical and chemical properties?
9. What does atomic radius and ionic radius really mean to you?
10. How does atomic radius vary in a period and in a group? How do you explain the variation?
11. What do you understand by isoelectronic species? Name a species that will be
isoelectronic with each of the following atoms or ions.
(i)
(ii) Ar
(iii)
(iv) Rb+
12. Consider the following species:
(a) What is common in them?
(b) Arrange them in the order of increasing ionic radii.
13. Explain why cations are smaller and anions larger in radii than their parent atoms?
14. What is the significance of the terms – ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?
Hint: Requirements for comparison purposes.
15. Energy of an electron in the ground state of the hydrogen atom isJ. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol-1.
16. Among the second period elements the actual ionization enthalpies are in the order Li < B < Be < C < O < N < F < Ne.
Explain why
(i) Be has higherthan B
(ii) O has lower than N and F?
17. How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?
18. What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?
19. The first ionization enthalpy values (in ) of group 13 elements are:
How would you explain this deviation from the general trend?
20. Which of the following pairs of elements would have a more negative electron gain enthalpy?
(i) O or F (ii) F or Cl