Q1.  Compare the radii of two species X and Y. Give reasons for your answer.  (i) X has 12 protons and 12 electrons  (ii) Y has 12 protons and 10 electrons. 

Q2. The atomic number of elements A, B, C, D and E are given below.







Atomic Number






From the above table, answer the following questions.

(i)  Which two elements are chemically similar?

(ii)  Which element is an inert gas?

(iii)  Which element belongs to 3rd period of periodic table?

(iv) Which element among these is a non-metal?

Q3.  ‘Hydrogen occupies a  unique position in modern periodic table’, Justify the statement.           

Q4.  An element Y has a total of three shells, with six electrons in its valence shell.

(i) What will be the atomic number of this element?

(ii) In which period will you find this element?

(iii) Name another element which belongs to the same group as this element.

Q5.  Atomic radii of the elements of the second period are given below:

Period 2 elements







Atomic Radii (pm)







(i) Arrange the elements in the decreasing order of their atomic radii.

(ii) Identify the element that restively has :

            (a) largest radius          (b) smallest radius

(iii) Give reasons for the variation in atomic radii.

Q6.  From the part of a periodic table, answer the following questions:























(i) Atomic number of oxygen is 8.  What would be the atomic number of fluorine?

(ii) Out of X and Q which element has larger atomic size? Give reason for your answer.

(iii) Out of Y and Z which element has smaller atomic size? Give reason for your answer.

Q7.  An element A reacts with oxygen to form A2O.

(i) State the number of electrons in the outermost orbit of A.

(ii) To which group of periodic table does A belong?

(iii) State whether A is a metal or non-metal.

Q8.  Two elements P and Q belong to the 3rd period of the modern periodic table and are in group 1 and group 2 respectively. Compare their following characteristics  in tabular form:

  • The number of electrons in their atoms
  • The sizes of their atoms
  • Their metallic character
  • Their tendencies to lose electrons
  • The formula of their oxides
  • The formula of their chlorides.

Q9. State the main aim of classifying elements. Which is the more fundamental property of elements that is used in the development of  Modern Periodic Table? Name and state the law based on this fundamental property.  On which side of the periodic table one can find metals, non-metals and metalloids?

Q10. An element ‘X’ with electronic configuration (2,8,2) combines separately with two radicals, (NO3 ) and (SO4)2−.

(i) Is ‘X’ a metal or a non-metal? Write the nature of its oxide.

(ii) Write the formula of the compounds of ‘X’ formed by the combination of these radicals. Are these compounds covalent or electrovalent?

Q11.  How   does   the  atomic   radius of  the  elements change on going

(i) from left to right in a period, and

(ii) down  a group

in the  Modern Periodic  Table  ?  Give reason in support of your answer.

Q12. What is meant by ‘group’ in the modern periodic table? How do the following change on moving from top to bottom in a group?

(i) Number of valence electrons

(ii) Number of occupied shells

(iii) Size of atoms

(iv) Metallic character of element

(v) Effective nuclear charge experienced by valence electrons.

Q13.  An element ‘X’ belongs to third period and  second group of the Modern Periodic Table.

(i) Write its electronic configuration.

(ii) Is it a metal  or non-metal? Why?

(iii) Write the formula of the compound formed when ‘X’ reacts with an element.

                   (a) Y of electronic configuration 2, 6 and 

                   (b) z with electronic configuration 2, 8, 7.

Q14. An element ‘X’ belongs to 3rd period and group 16 of the Modern Periodic Table.

(i) Determine the number of valence electrons and the valency of ‘X’.

(ii) Molecular formula of the compound when ‘X’ reacts with hydrogen and write its electron dot structure.

(iii) Name the element ‘X’  and state whether it is metallic or non-metallic.

Q15. Two elements X  and  Y belong to group  1 and  2 respectively in the same period of the periodic table. Compare  these elements with respect to :

(i) number of electrons in their outermost orbit

(ii) their valencies

(iii) metallic character

(iv) their atomic size

(v) formula  of their chlorides

(vii) formula  of their sulphates.

Q16. Given  below  are  some  elements of the modern periodic  table :

4Be, 9F, 14Si, 19K, 20Ca.

(i) Select the element that has one electron in the outermost shell and write its electronic configuration.

(ii) Select two elements that belong to the same group. give reason for your answer.

(iii) Select two elements that belong to the same period. Which one of the two has bigger atomic size?

Q17.  State the difference between modern periodic table and Mendeleev’s periodic table.

Q18. (a) Can the following groups of elements be classified as Dobereiner’s triad?

                        (i). Na, Si, Cl        (ii) Be, Mg, Ca

Explain by giving reason.

(Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40)

         (b) Upto which element, the law of octaves was found to be applicable?

Q19.       Four elements A, B, C and D have atomic numbers 12, 13, 14 and  15 respectively. Answer the following questions giving reasons.

(i)  What is the valency of B?

(ii)  Classify these elements as metals and non-metals.

(iii)  Which· of these elements will form the most basic oxide?

Q20.       X is an element of modern periodic table. It is surrounded by elements having atomic number  17, 34, 36 and  53.

(i)   What is the atomic number of X?

(ii)   Predict its position in the periodic table.

(iii) Which among these do not belong to the same Group?


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