X CBSE Practice Work sheet

CBSE Board Questions

1. (a) What are metalloids ? Write any two examples.

 (b) Given below are some of the elements of first group Li, Na, K (Their atomic numbers are 3,11,19 respectively and they belong to 2nd 3rd and 4th period respectively) Arrange these in the decreasing order of metallic character exhibited by them. 

2. What are amphoteric oxides? Choose the amphoteric oxide from among the following

oxides :– Na2O, ZnO, Al2O3, CO2, H2O

3. Study the variation in the atomic radii of first group elements given below and arrange

them in increasing order :–

Group I element          Na       Li       Rb          Cs                  K

Atomic Radii P.M      86      152    244         262                 231

4. An element X has the electroic configuration as 2, 8, 7 :–

(a) What is the atomic number of the element?

(b) What will be the formula of its compound formed with Na?

(c) What is the name given to the family of this element?

5. How do you calculate the valence of the element from its electronic configuration? What is the valence of Mg with atomic number 12 and sulphur with atomic number 16? How does the valence vary in going down in a group?

6. Atomic radii of the elements of the period II are as follows:–

Period II elements :        Be         B      O      N     C       Li

Atomic Radius :           111        88     66     74    77     152

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

(ii) How does the atomic size vary on moving from left to right in a period? Explain why?

(iii) How will the tendency to lose electrons will vary on moving from left to right in this period II?

7. Oxygen (O, 8) and sulphur (S, 16) belong to group 16 of the periodic table:-

(i) Write the electronic configuration and valence of these two elements?

(ii) Which among these will be more electronegative? Why?

8. Given below are the atomic radii of some elements of second period.

Element		B	O	N	C
Atomic Radius in pm	88	66	74	77

Arrange these elements in the increasing order of their atomic number . Give reason for your answer.

9. Two elements ‘A’ and ‘B’ belong to group 1 and 2 respectively in the same period.

Compare them with respect to :–

(a) Number of valence electrons.

(b) Valency

(c) Metallic character

(d) Size of atom

(e) Formulae of their oxides.

10. (a) Atomic radius of hydrogen is 37pm. Express it in meters. (b) How does atomic size vary in a group and in a period ?

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

1 Hydrogen	2	13	14 Carbon			15	16 Oxygen		17 Fluorine
X				P				Q
Y								R
Z								T

(a) Atomic number of oxygen is 8. What would be the atomic number of, Fluorine ?

(b) Out of ‘X’ and ‘Q’ which element has larger atomic size. Give reason for your answer Fluorine.

(c) Out of ‘Y’ and ‘Z’ which element has smaller atomic size. Give reason for your answer.

12.State Modern Periodic Law. Name the two elements of first period.

13.Two element X, Y and Z belong to 17th group but to 2nd,3rd and 4th period respectively. Number of valence electrons in Y is 7. Find the number of valence electrons in X and Z.

14. How does the metallic character of the elements vary (i) in a group (ii) in a period of the modern periodic table ?

15. Na, Mg, Al and P belong to 3rd period but are placed in first, second, thirteenth and fifteenth group. Number of shells occupied in Mg is three. What is the number of occupied shells in Na, Al and P. Give reason for your answer.

Q. What is the number of elements in first , second and third period of the periodic table? Give reason for your answer.