#### Atomic Structure Book Back Questions

9th Standard

Reg.No. :
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Science

Time : 00:45:00 Hrs
Total Marks : 30
3 x 1 = 3
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 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

4. 4 x 1 = 4
5. Calcium and Argon are examples of a pair of __________

()

isobars

6. _________isotope is used in the treatment of goiter

()

iodine 131

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

()

4

8. The valency of Argon is ________

()

zero

9. 3 x 1 = 3
10. In an atom, electrons revolve around the nucleus in fixed orbits

(a) True
(b) False
11. Electrons have negligible mass and charge.

(a) True
(b) False
12. The maximum number of electron in L Shell is 10

(a) True
(b) False
13. 3 x 2 = 6
14. Name an element which has the same number of electrons in its first and second shell

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

17. 3 x 3 = 9
18. Methane burns in oxygen to form carbon dioxide and water vapour as given by the equation
CH4(g) + 2O2(g) ➝ CO2(g)+ 2H2O(g)
Calculate: (i) the volume of oxygen needed to burn completely 50 cm3 of methane and (ii) the volume of carbon dioxide formed in this case.

19. State the law of multiple proportions

20. Calculate the number of neutrons, protons and electrons (i) atomic number 3 and mass number 7 (ii)atomic number 92 and mass number238

21. 1 x 5 = 5
22. Explain the postulates of Bohr’s atomic model