Assignment - Periodic Classification of Elements, Class 10, Science PDF Download

FILL IN THE BLANKS :-
1. The horizontal rows in the periodic table are known as ....................

2. The vertical columns of in the periodic table are known as ...............
3. A very short period contains ........ elements.
4. The element having electronic configuration (2, 8, 3) belongs to ............ group.
5. In a group atomic radii ............. from top to bottom and in a period atomic radii ............ from left to right.
6. Size of Na+ is ............... than sodium atom.
7. Size of Cl– is .............. than Cl atom.
8. An element 'B' belongs to the seocnd period and group 13, formula of its oxide is ....................
9. Elements in the same group have similar .................
10. Elements in the same group have similar ................ in their outer most shell.
11. The alkaline earth metal with the smallest atomic number is ...................
12. A, B & C are the elements of the Doberiner's triads. If the atomic mass of A is 7 and that of B is 23, then
the atomic mass of 'C' will be .................
13. When Mendeleev made the periodic table the number of elements discovered till then were ...........
14. Among alkali metal.....................has the smallest atomic radius.
15. Among halogens.....................has the smallest atomic radius.
16. The amount of energy released when a neutral gaseous atom gains one electron is called .....................
17. The energy required to remove an electron from an isolated gaseous atom is called .....................
18. Non-metallic character ..................... from left to right in a period.
19. Metallic character ..................... down a group.
20. Ionisation energy ..................... down a group and ..................... along a period.
21. Atomic size ..................... from left to right in a period.

ANSWER FOLLOWING QUESTIONS :-
1. Why did Mendeleev leave some gaps in the periodic table of elements ? Give your answer with examples.

2. Explain why the properties of the 8th element are repeated in case of elements arranged in 2nd and 3rd period of the long from of the periodic table.

3. Where in period 3 of the modern periodic table do we find :

1.  non-metals
2. elements forming negative ions
3. elements with high melting points
4. elements forming positive ions
5. metals
6. elements with low boiling points ?

Mention their atomic numbers only.

4. If you look at the long form of periodic table, you will find that the elements Li, B, C, N, O, F and Ne are present in the second period. Write down their electronic configurations.

5. Examine elements of the third period and classify them as metals and non-metals.

6. Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to Group 15 of periodic table. Write the electronic configuration of these elements. Which of these will be more electronegative ? Why ?

7. How could the modern Periodic Table remove various anomalies of Mendeleev's Periodic Table ?

8. Name two element you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?

9. Name

1. Three elements that have a single electron in their outermost shells.
2. Two elements that have two electrons in their outermost shells.
3. Three elements with filled outermost shells.

10. (a) Lithium, sodium, potassium are all metal that react with water to liberate hydrogen gas is thre any similarity in the atoms of these atoms.
(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common ?

11. In the Modern Periodic Table, which are the metals among the first ten elements ?

12. By considering their position in the periodic table, which one of the following elements would you expect to have maximum metallic characteristic.
         Ga             Ge          As            Se              Be

13. Which of the following statements is not a correct statement about the trends when going from left to right across
the periods of periodic table.

1. The elements become less metallic in nature.
2. The number of valence electrons increase
3. The atoms lose their electrons more easily
4. The oxides become more acidic

14. Element X forms a chloride with the formula XCl2, which is a solid with a high melting point X woud most likely
be in the same group of the periodic table
(a) Na

(b) Mg

(c) Al

(d) Si

15. (a) What property do all elements in the same column of the periodic table as boron have in common ?
(b) What property do all elements in teh same column of the periodic table as fluorine have in common ?

16. An atom has electronic configuration 2.8.7
(a) What is the atomic number of this element ?
(b) To which of the following elements would it be chemically similar ? (Atomic number are given in parenthese)
N(7)       F (9)           P(15)          Ar(18)

ANSWER KEY

1. Periods

2. Groups

3. 2

4. 13

5. Increases, decreases

6.Smaller

7. Larger

8. B₂O₃

9. Properties
10. electrons

11. 4

12. 15

13. 63 elements

14. Li

15. F

16. Electron affinity
17. Ionisation energy

18. Increases

19. Increases

20. Decreases, Increases

21. Decreases