Class 9 Chemistry Chapter Structure of Atoms Important mcqs

1. Atoms are so ______ that they can only be visualized by a scanning tunneling microscope.

A. large

B. charged

C.small

D.electronic

Answer: C

Note:

A scanning tunneling microscope (STM) is a type of microscope used to capture atomic-level images of surfaces.

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2. In 1911 ____ performed an experiment in order to know the arrangement of electrons and protons in an atom.

A. Schrodinger

B. Rutherford

C. Bohr

D. Newton

Answer: B

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3. Rutherford bombarded a very thin gold foil with ____ particles.

A. Alpha

B. Beta

C. Gamma

D. Tera

Answer: A

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4. Rutherford used alpha particles from the disintegration of _____

A. Boron

B. Silicon

C. Tin

D. Polonium

ANSWER : D

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5. In Rutherford’s experiment only one in one million (Alpha particle) was deflected through an angle greater than ___ from their straight path.

A. 97°

B. 90°

C. 180°

D. 100°

Answer: B

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6. On the basis of his (Rutherford) experiment he proposed a _____ model for an atom.

A. Geological

B. Mathematical

C. Planetary

D. None of these

Answer: C

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7. According to classical physics electron being charged particle will emit energy ____ while revolving around the nucleus.

A. Continuously

B. Discontinuously

C. Slowly

D. Both b & c

Answer: A

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8. If a revolving electron emits energy continuously it should form a _______ spectrum.

A. Line

B. Continuous

C. Atomic

D. None of the above

Answer: B

Note !!

• When white light is passed through a prism it is scattered into 7 colours.
• Continuous spectrum:
• In a continuous spectrum, different colours are diffused into one another and not separated by dark spaces.
• Line Spectrum:
• In the line spectrum, different colours are not diffused into one another and are separated by dark spaces.

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9. According to Bohr each orbit has a ____ energy.

A. Fixed

B. Variable

C. Large

D. Minute

ANSWER: A

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10. According to Bohr energy of an electron is directly proportional to its ___ from the nucleus.

A. size

B. distance

C. electronegativity

D. none of the above

Answer: B

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11. Value of Plank’s constant is ____

A. 6.626×10^-34 J.s

B. 5.52×10³⁴J.s

C. 9.011×10^-31J.s

D. 1.6011×10¹⁶ J.s

Answer: A

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12. An electron jumps from K shell to L shell in this the electron ____ energy.

A. emits

B. donates

C. absorbs

D. none of these

Answer: C

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13. Electron present in a particular orbit does not ____ energy.

A. absorbs

B. radiates

C. emits

D. all of these

Answer: D

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14. According to Bohr mvr =

A. nh/2V

B. nh/4π

C. nh/4V

D. nh/2π

ANSWER: D

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15. Which one of the following is correct according to Bohr’s model?

A. ΔE =E₃ – v

B. ΔE=E₂ –E₁

C. ΔE=F.s

D. All of these

Answer: B

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16. Which of the following is true for isotopes?

A. they have the same number of neutron

B. they have the same atomic mass

C. they have the same atomic number

D. all of these

Answer: C

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17. Isotopes have different atomic mass due to ____

A. different number of electrons

B. different number of protons

C. different number of neutron

D. different atomic number

Answer: C

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18. Isotopes are ____ alike.

A. chemically

B. physically

C. neutral

D. none of the above

ANSWER: A

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19. Physical properties of an element depend upon its _____.

A. Atomic number

B. Protons

C. Electrons

D. Atomic mass

Answer 😀

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20. Atomic mass can also be called ___.

A. electron affinity

B. mass number

C. nucleon number

D. both b & c

Answer: D

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21. The first man to use the word “isotope” was ___.

A. Einstein

B. Sodday

C. Newton

D. G.N Lewis

ANSWER: B

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22. Hydrogen has __ isotopes.

A. 4

B. 6

C. 3

D. 5

Answer: C

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23. Tritium has how many neutrons?

A. 0

B. 1

C. 2

D. 3

Answer: C

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24. Melting point of heavy water is __ °C.

A. 0

B. 3.81

C. 4.3

D. 5.4

Answer: B

Note!!

Heavy water (D2O) is also referred to as deuterium oxide.

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25. The number of isotopes of carbon are ___

A. 2

B. 4

C. 3

D. 6

Answer: C

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26. Natural abundance of C-12 = __

A. 98.8%

B. 99%

C. 97%

D. 99.7

Answer: A

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27. Chlorine has how many isotopes?

A. 3

B. 4

C. 5

D. 2

Answer: D

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28.Chlorine-37 occurs in nature at about ___%.

A. 75.78%

B. 24.23%

C. 35%

D. 65%

Answer: B

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29. Chlorine is fairly __ in water.

A. insoluble

B. soluble

C. reactive

D. none of these

Answer: B

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30. Chlorine is a greyish ___ gas with a sharp pungent irritating smell.

A. pink

B. blue

C. red

D. yellow

Answer: D

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31. If Uranium(²³⁴U) has 92 protons then it has __ number of neutrons.

A. 142

B. 134

C. 122

D. none of the above

Answer: A

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32. Radioactive iodine -131 is used as a tracer in diagnosing ___ problem.

A. ulcer

B. lungs

C. heart

D. thyroid

Answer: D

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33. Cobalt-60 is commonly used to irradiate ___ Cells in the hope of killing or shrinking the tumors.

A. nerve

B. red blood cells

C. cancer

D. white blood cells

Answer : C

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34. As the value of n___ the distance of an electron from the nucleus and the energy of the shell increases.

A. increases

B. decreases

C. stays the same

D. All of these

Answer: A

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35. s sub-shell can accommodate maximum _ electrons.

A. 3

B. 4

C. 2

D. 6

Answer: C

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36. f sub-shell can accommodate maximum electrons.

A. 14

B. 12

C. 10

D. 8

Answer: A

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37. 1s < 2s < 2p < 3s < 3p<4s < __ .

A. 3d

B. 4s

C. 4p

D. 5s

Answer: A

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38. ¹¹Na=1s²,2s²,2p⁶ __ .

A. 3p¹

B. 3d¹⁰

C. 4s¹

D. 3s¹

Answer: D

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39. Using Bohr’s formula i.e 2n², determine the number of electrons that can be added into M – shell .

A. 12

B. 18

C. 8

D. 28

Answer: B

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40. If an element has 20 electrons how many sub-shells will it have?

A. 2

B. 3

C. 4

D. 6

Answer: D

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41.___ subshell is spherical shaped.

A. s

B. p

C. d

D. f

Answer: A

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42. ___ subshell has a very complicated shape.

A. s

B. p

C. d

D. f

Answer: D

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43. Heavy water is made by using ___.

A. protium

B. deuterium

C. tritium

D. none of these

Answer: B

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44. Boiling point of water is ___ .

A. 101°C

B. 100°C

C. 102°C

D. 103°C

Answer: B

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45. L shell can accommodate a maximum of ___ electrons.

A. 3

B. 2

C. 8

D. 6

Answer: C

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46. Which one of the following shell has the lowest energy?

A. L

B. N

C. M

D. K

Answer: D

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47. How many neutrons are there in chlorine – 37 if it has 17 electrons?

A. 21

B. 20

C. 19

D. 12

Answer: B

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48. d Sub shell has ___ shape.

A. spherical

B. dumbell

C. double dumbell

D. none of them

Answer: C

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49. Keeping in mind the Auf Bau principle the electron will first enter into which subshell?

A. 3s

B. 1s

C. 2s

D. 4s

Answer: B

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50. How many neutrons are there in ²⁷M if its atomic number is 13?

A. 12

B. 13

C. 14

D. 16

Answer: C

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