#### Atomic Structure - Important Question Paper

9th Standard

Reg.No. :
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Science

Time : 01:00:00 Hrs
Total Marks : 50

Part A

5 x 1 = 5
1. Among the following the odd pair is

(a)

8O18, 17cl37

(b)

18Ar40,7N14

(c)

14Si30, 15pd31

(d)

24cr54, 19K39

2. Change in the number of neutrons in an atom changes it to

(a)

an ion

(b)

an isotope

(c)

an isobar

(d)

another element

3. The term nucleons refer to

(a)

Protons and electrons

(b)

only Neutrons

(c)

electrons and neutrons

(d)

Protons and neutrons

4. The number of protons, neutrons and electrons present respectively in $_{ 35 }^{ 80 }{ Br }$

(a)

80, 80, 35

(b)

35, 55,80

(c)

35, 35, 80

(d)

35, 45, 35

5. The correct electronic configuration of potassium is

(a)

2,8,9

(b)

2,8,1

(c)

2,8,8,1

(d)

2,8,8,3

6. Part B

5 x 1 = 5
7. Calcium and Argon are examples of a pair of __________

()

isobars

8. Total Number of electrons that can be accommodated in an orbit is given by-------

()

2n2

9. _________isotope is used in the treatment of goiter

()

iodine 131

10. The number of neutrons present in $_{ 3 }^{ 7 }{ Li }$ is ------

()

4

11. The valency of Argon is ________

()

zero

12. Part C

6 x 2 = 12
13. Name an element which has the same number of electrons in its first and second shell

14. Write the electronic configuration of K+ and Cl

15. Compare the charge and mass of protons and electrons.

16. For an atom ‘X’, K, L and M shells are completely filled. How many electrons will be present in it?

18. Arrange the following in the increasing order of atomic number
Calcium, Silicon, Boron, Magnesium, Oxygen, Helium, Neon, Sulphur, Fluorine and Sodium

19. Part D

6 x 3 = 18
20. An atom has 11 protons, 11 electrons and 12 neutrons. What is the atomic number and the name of the element?

21. Calculate the atomic number of an element whose mass number is 39 and number of neutrons is 20. Also find the name of the element

22. State the law of multiple proportions

23. List the uses of isotopes?

24. What is isotone? Give an example

25. Draw the structure of oxygen and sulphur atoms