Q1. Upto which element, the  Law of Octaves was found to be applicable?

Q2. Why are noble gases missing from Newlands’ Octaves?

Q3. Atomic number is considered to be a more appropriate parameter than atomic mass for classification of elements in a periodic table. Why?

Q4. Out of Na, Al, Si, P which element exhibits maximum number of valence electrons?

Q5. Elements  A,   B,  C  and   D  have atomic numbers  1,  8,   11  and    19  respectively. Choose the odd element and give reason for your answer. 

Q6. Write the correct increasing order of the atomic radii of O, F and N.

Q7. Which group of elements will form an acidic oxide?

Q8. An element X is in  second period of group 16 of the periodic table. Is it metal or non-metal? Give reason for your answer.

Q9. Write two reasons responsible for late discovery of noble gases. 

Q10. Why hydrogen should be placed in Group I?

Q11. State one reason for placing  Mg and   Ca in the same group of the periodic table.

Q12. The atomic numbers of three elements A, B and C are 12, 18 and 20 respectively. State giving reason, which two elements will show similar properties.

Q13. The atomic number of three-element X, Y and  Z are 3, 11 and 17 respectively. State giving reason which two elements will show similar chemical properties.

Q14. How does the electronegativity changes as we move from left to right across a period?

Q15.  What is meant by periodicity in properties of elements with reference to periodic table?

Q16. Why is lithium atom smaller than potassium atom?

Q17. What is the basis for the classification of modern periodic table?

Q18. Name the two elements whose valencies are equal to their group number.

Q19. Why does silicon has valency  4 and chlorine  1?

Directions (Q. Nos. 10 – 14)  In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as:

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.            ·

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e) If both Assertion and Reason are false.

Q10. Assertion: Atomic size of potassium is greater than that of sodium.

           Reason: As we go down the group, atomic radius increases.

Q11. Assertion: Alkali metals have smallest size in a period.

            Reason: They are at the extreme left of the periodic table.

Q12. Assertion: Nobel Elements were not included by Mendeleev’s Periodic Table.

            Reason: Mendeleev did not know where to place in his Periodic Table.

Q13. Assertion: Electronegativity decreases from left to right along a period in the Modern Periodic Table.

            Reason: As electron is added to the same shell when moving from left to right along a period, the force of attraction increases between the nucleus and the electron on the last shell.

Q14. Assertion: Atomic Mass of certain elements are expressed in fraction taking in account the availability of its various isotopes.

            Reason: Isotopes of an element have the same atomic mass but different atomic number.

Q15. When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

(a ) No reaction takes place.

(b) A  colourless gas with pungent smell is released with brisk effervescence.

(c) A  brown coloured gas is released with brisk effervescence.


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