Atomic Structure and Cathode Ray Tubes

Test your understanding of the fundamental particles of an atom and the experiment that led to the discovery of the electron.

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1. According to the text, who is credited with coining the term 'atom'?

J.J. Thomson Rutherford John Dalton Dr. A.O. Rajee

Explanation: The text explicitly states, 'John Dalton coined the term atom.'

2. What two conditions are required for the production of cathode rays in a discharge tube, as described in the text?

High voltage and high pressure Low voltage and high pressure High voltage and very low pressure Low voltage and very low pressure

Explanation: The section on the discovery of the electron states, 'when a high voltage is applied... at a very low pressure, some invisible radiations are emitted from the cathode.'

3. Why does no electric current flow through the discharge tube when the gas pressure is at 1 atm?

The voltage is too low. The glass is an insulator. The gases are poor conductors of electricity. The electrodes are too far apart.

Explanation: The text states, 'when the gas pressure in the tube is 1 atm, no electric current flows through the tube. This is because the gases are poor conductor of electricity.'

4. Based on the text, what is the fundamental composition of cathode rays?

High-speed protons emitted from the anode Ionized gas molecules Invisible light radiation High-speed electrons emitted from the cathode

Explanation: Under 'Origin of Cathode rays', the text clarifies, 'Cathode rays are high-speed electrons emitted first from the cathode.'

5. According to the document, why is an atom considered electrically neutral?

It has no charged particles. The number of protons equals the number of neutrons. The number of protons equals the number of electrons. It is indivisible and indestructible.

Explanation: The text states, 'In fact, the atom as the whole is electrically neutral as number of protons in it is equal to number of electrons.'

6. In the diagram of the discharge tube experiment, in which direction do the cathode rays travel?

From the anode (+) to the cathode (-) From the cathode (-) to the anode (+) From the vacuum pump to the electrodes Outwards from the center of the tube

Explanation: The diagram shows the cathode labeled with a negative sign and the anode with a positive sign. The dotted lines representing cathode rays originate at the cathode and move towards the anode.

7. What visible effect, shown in the diagram, indicates the presence of cathode rays?

A red glow around the cathode A faint green glow on the tube wall Sparks between the electrodes The gas in the tube turns blue

Explanation: The diagram has a label pointing to the end of the tube opposite the cathode that reads 'Faint green glow', which is caused by the bombardment of the glass by the cathode rays.

8. Which scientist is named in the text for their observations of cathode rays?

John Dalton Dr. A.O. Rajee J.J. Thomson Rutherford

Explanation: The section 'Discovery of electron - study of Cathode rays' begins by crediting the observation to J.J. Thomson.

9. According to the introductory paragraph, modern physics finds it difficult to create an accurate verbal portrayal of the electron because of its:

Extremely large size Slow, predictable movement Mathematical simplicity Mathematical complexity and unusual nature

Explanation: The introduction states, 'The modern description of the electron is based on complex mathematics... The mathematical complexity alone makes an accurate verbal portrayal of the electron challenging...'

10. Which of the following is listed as one of the 'Aims' of the lesson?

To introduce Dalton's atomic theory To introduce Thomson's and Rutherford Atomic model To explain the nature of nuclear fusion To calculate the mass of an electron

Explanation: The second point under the heading 'AIM' is '2) To introduce Thomson's and Rutherford Atomic model'.

11. According to the text, which of the following is NOT a property of cathode rays?

They cause ionization of the gas through which they pass. They are made up of material particles. Their nature depends on the gas inside the discharge tube. They produce a heating effect.

Explanation: Point (x) under 'Properties of Cathode rays' explicitly states that 'The nature of the cathode rays does not depend upon the nature of the gas, taken in the discharge tube and the nature of cathode material.'

12. Who first discovered the presence of positive rays (anode rays)?

Ernest Rutherford Goldstein A.O. Rajee J.J. Thomson

Explanation: The text states, 'Goldstein discovered the presence of positive rays. He performed an experiment in which he took perforated cathode...'

13. In the experiment for the production of anode rays, why is the cathode perforated?

To allow the anode rays to pass through it. To increase the speed of the cathode rays. To generate X-rays more effectively. To cool down the discharge tube.

Explanation: The text describes that in Goldstein's experiment, 'new rays were coming from the side of anode and passing through the hole in the cathode'. The perforations (holes) allow these rays to travel to the other side for detection.

14. How are anode rays (or positive rays) formed?

By electrons being emitted from the anode. By gas atoms in the tube losing their electrons. By the breakdown of the cathode material. By the vacuum pump creating positive particles.

Explanation: Under the section 'Origin of anode or positive rays', the text explains that 'In the discharge tube the atoms of gas lose negatively charged electrons. These atoms, thus, acquire a positive charge.'

15. Who is credited with the discovery of the proton by proving it is a fundamental particle present in the nuclei of all atoms?

Goldstein A.O. Rajee Ernest Rutherford The text does not say

Explanation: While Goldstein discovered positive rays, the text specifies, 'The discovery of the proton is credited to Ernest Rutherford, who proved that the nucleus of the hydrogen atom (i.e. a proton) is present in the nuclei of all other atoms...'

16. What is a key difference between anode rays and cathode rays mentioned in the text?

Anode rays travel in curves while cathode rays travel in straight lines. Anode rays are negatively charged while cathode rays are positively charged. The speed of anode rays is much less than that of cathode rays. Anode rays cannot affect photographic plates, but cathode rays can.

Explanation: The very last point under 'Properties of Anode rays' states, 'However, their speed is much less than that of the cathode rays.'

17. What happens when cathode rays strike a hard metal target like tungsten?

They produce green fluorescence. They produce X-rays. They are completely absorbed. They turn into anode rays.

Explanation: Point (vi) of 'Properties of Cathode rays' says, 'They produce X-rays when they strike against the surface of hard metals like tungsten, molybdenum etc.'

18. The positively charged particle produced from hydrogen gas is specifically called a:

Canal ray Electron Anode Proton

Explanation: The text explains under 'Origin of anode or positive rays': 'The positively charged particle produced from hydrogen gas was called the proton. H → H⁺(proton) + e⁻'.

19. What characteristic of cathode rays is described as being 'constant'?

Their speed Their penetrating power The ratio of charge (e) to mass (m) The intensity of the fluorescence they produce

Explanation: Point (xi) under 'Properties of Cathode rays' states, 'For each cathode rays, the ratio of charge (e) to mass (m) is constant.'

20. In the diagram for the production of anode rays, what is the purpose of the 'ZnS coating'?

To act as the anode. To absorb stray electrons. To produce fluorescence when struck by anode rays. To help maintain the vacuum.

Explanation: The text describes that anode rays 'gives fluorescence on the opposite glass wall coated with zinc sulphide.' The ZnS (zinc sulphide) coating serves as a screen to make the invisible rays visible.

21. Who is credited with the discovery of the electron?

Ernest Rutherford Chadwick J.J. Thomson Millikan

Explanation: The section on the electron begins with 'Electron is a universal constituent discovered by the J.J. Thomson.' The summary table also lists J.J. Thomson as the discoverer of the electron.

22. According to the text, which experiment determined the charge of an electron?

Gold foil experiment Cathode ray experiment Beryllium bombardment Millikan's oil drop experiment

Explanation: Under the 'Electron' section, the first bullet point for 'Charge' states: 'It was determined by Millikan by oil drop experiment'.

23. What is the charge of a neutron as described in the document?

-1.6022x10⁻¹⁹ C +1.6022x10⁻¹⁹ C Zero +1

Explanation: The section on the neutron states it is a 'Charge less or neutral particle.' The summary table also lists its charge as 'Zero'.

24. The text states that a proton is how many times heavier than an electron?

1/1837th times 1837 times 0.18% times 9.58x10⁴ times

Explanation: In the 'Proton' section, the bullet point for 'Mass' mentions, 'It is 1837 times heavier than an electron.'

25. Which elementary particle is described as the 'heaviest and least stable'?

Electron Proton Neutron Alpha Particle

Explanation: The last bullet point in the 'Neutron' section explicitly states, 'Among all the elementary particles neutron is the heaviest and least stable.'

26. Chadwick discovered the neutron by bombarding which element with high-speed alpha particles?

Carbon (C) Helium (He) Hydrogen (H) Beryllium (Be)

Explanation: The text describes the discovery of the neutron as 'by bombarding Be atom with high speed α-particles.' The nuclear equation provided (⁴Be⁹ + ₂He⁴ → ₆C¹² + ₀n¹) also shows Beryllium as the target.

27. What is the mass of a proton in kilograms (kg) according to the summary table?

9.109x10⁻³¹ kg 1.672x10⁻²⁷ kg 1.675x10⁻²⁷ kg 1.672x10⁻²⁴ kg

Explanation: The summary table, in the column for 'Proton' and the row for 'Mass', lists the value as '1.672x10⁻²⁷ kg'.

28. Based on the text, the nature and charge-to-mass ratio of anode rays depend on what?

The material of the cathode The pressure inside the tube The gas taken in the discharge tube The strength of the electric field

Explanation: Point (iv) in the introduction states, 'The nature of anode rays depends on the gas taken in the discharge tube.' Point (v) adds that the charge-to-mass ratio is different for different gases.

29. Where is the electron located within an atom, according to the summary table?

In the nucleus Outside the nucleus Both inside and outside the nucleus The location is not specified

Explanation: In the last row of the summary table, labeled 'Location', the entry for the 'Electron' column is 'Outside the nucleus'.

30. What is the value of the charge on one mole of electrons, also known as one faraday?

1.602x10⁻¹⁹ coulombs 96500 coulombs 1.76x10⁸ coulombs/gm 0.55 mg

Explanation: Under section '1) Electron', a bullet point states: 'Charge on one mole of electron is 96500 coulombs or 1 faraday.'

31. According to the text, Thomson's atomic model describes an atom as:

A sphere of positive charge with electrons embedded in it. A dense positive nucleus with electrons orbiting it. A sphere of negative charge with positive particles embedded in it. An indivisible, solid particle.

Explanation: The text for Thomson's Atomic Model states, 'an atom is a sphere of positive charge having a number of embedded electrons in it...'

32. What is a common analogy used to describe Thomson's Atomic Model, as mentioned in the document?

Solar system Billiard ball Plum pudding or watermelon Onion layers

Explanation: The text says, 'This model is compared with a water melon in which seeds are embedded or pudding in which raisins are embedded. Therefore, this model, sometime called watermelon model or raisin or plum pudding model.'

33. What was a major limitation of Thomson's Atomic Model according to the image?

It couldn't explain the existence of isotopes. It failed to explain the results of Rutherford's scattering experiment. It didn't account for the mass of the atom. It violated the law of conservation of energy.

Explanation: Under the 'Limitation' section for Thomson's model, the text states: 'This model failed explain the results of scattering experiment of Rutherford and the stability of atom.'

34. In Rutherford's scattering experiment, what kind of particles were bombarded onto the thin metal foil?

Beta particles Electrons Alpha particles Neutrons

Explanation: The text describes Rutherford's experiment as an 'α-ray scattering experiment' and mentions bombarding the foil with a 'beam of fast moving radioactive particles' (α-particles).

35. What was the purpose of the zinc sulphide (ZnS) screen in Rutherford's experiment?

To generate the alpha particles. To hold the gold foil in place. To absorb stray radiation. To detect the alpha particles after they hit the foil.

Explanation: The text states that the presence of α-particles was 'detected with the help of a circular zinc sulphide screen. The point at which an α particle strikes this screen, a flash of light is given out.'

36. What was the main observation from Rutherford's experiment as described in the 'Observations and Conclusions' section?

All alpha particles were deflected at 90-degree angles. The alpha particles were completely absorbed by the foil. A few alpha particles bounced straight back. Most of the alpha particles passed through the foil without any deflection.

Explanation: The first point under 'Observations and Conclusions' states: 'Most of the α-particles passed through the gold foil without any deflection from their original path.'

37. Based on the observation that most alpha particles passed straight through the foil, what was concluded about the structure of an atom?

The atom is mostly empty space. The atom is a solid, impenetrable sphere. The positive charge is evenly distributed throughout the atom. The atom is composed of smaller, neutral particles.

Explanation: The text concludes from the main observation that 'The atom has largely empty space as most of the α-particles passed through the foil undeflected.'

38. Which material was NOT mentioned as a potential thin foil in Rutherford's experiment?

Gold Silver Platinum Aluminum

Explanation: The text specifies that Rutherford used 'thin foils of metals like gold, silver, platinum or copper'. Aluminum is not listed.

39. According to the diagram of Rutherford's experiment, where did the alpha particles originate?

From the gold foil From a radioactive source inside a lead block From the zinc sulphide screen From a particle accelerator

Explanation: The text mentions the particles 'originated from a lead block,' and the diagram shows a 'radioactive source' from which the 'beam of alpha particles' emerges.

40. What happens when an alpha particle strikes the zinc sulphide screen in Rutherford's setup?

An audible click is produced. The screen changes color. A flash of light is given out. The screen becomes electrically charged.

Explanation: The description of Rutherford's Atomic Model explicitly states, 'The point at which an α particle strikes this screen, a flash of light is given out.'

41. According to Rutherford's model as described in the text, what is responsible for the majority of an atom's mass?

The electrons revolving in orbits The empty space within the atom The small, positively charged nucleus at the center The extra nuclear part

Explanation: The text explicitly states, 'The entire mass of the atom is concentrated in the nucleus' and 'As the nucleus of the atom is responsible for the mass of the atom...'

42. Why is an atom considered electrically neutral in Rutherford's model?

Because electrons and the nucleus continuously collide. Because the nucleus has no charge. Because the number of electrons equals the number of units of positive charge in the nucleus. Because the empty space cancels out the charge.

Explanation: Point 4 under 'According to Rutherford' states, 'The number of extra nuclear electrons is equal to the number of units of positive charge in the nucleus. Therefore the atom is electrically neutral.'

43. Rutherford's atomic model is often called the 'planetary model' because it resembles the solar system. In this analogy, what do the electrons represent?

The Sun Comets The planets The vacuum of space

Explanation: The text mentions the resemblance to the solar system. In this analogy, the central, massive nucleus is like the Sun, and the electrons revolving around it are like the planets.

44. What is the primary drawback of Rutherford's model, according to Maxwell's electromagnetic theory?

The atom contains too much empty space to be stable. The nucleus is too small and dense. An orbiting electron should continuously lose energy, emit radiation, and spiral into the nucleus. The electrostatic forces are too weak to hold the atom together.

Explanation: The 'Drawbacks' section explains that according to Maxwell's theory, a charged particle like an electron, when moving under an attractive force, should lose energy as radiation and ultimately 'fall into the nucleus thereby making the atom unstable.'

45. If electrons in an atom lost energy continuously as Rutherford's model implies, what kind of spectrum would be observed?

A continuous spectrum A spectrum with well-defined lines No spectrum at all An absorption spectrum only

Explanation: The text states in the second drawback, 'If the electrons lose energy continuously, the spectrum is expected to be continuous...' This contradicts the actual observation of line spectra.

46. In Rutherford's model, what part of the atom is responsible for most of its volume?

The nucleus The protons The electrostatic field The extra nuclear part where electrons are present

Explanation: Point 6 states, 'There is an empty space around the nucleus called extra nuclear part... the extra nuclear part is responsible for its volume.'

47. What key observation from the alpha-particle scattering experiment led to the conclusion of a dense, positively charged nucleus?

Most alpha particles passed straight through the atom. A few alpha particles were deflected at large angles or bounced back. All alpha particles were slightly deflected. The alpha particles were completely absorbed.

Explanation: The text mentions that a few alpha particles are deflected at large angles or even back along their path 'Bcz there is heavy positive charge at the center of the atom'.

48. Which of the following forces is responsible for holding the electrons in their orbits around the nucleus in Rutherford's model?

Gravitational forces Magnetic forces Electrostatic forces of attraction Strong nuclear forces

Explanation: Point 4 mentions that 'Electrons and the nucleus are held together by electrostatic forces of attraction.'

49. What is the ultimate fate of an electron in Rutherford's model when considering the principles of classical electromagnetic theory?

It achieves a stable, permanent orbit. It is ejected from the atom. It stops moving and hovers in place. It follows a spiral path and falls into the nucleus.

Explanation: The first drawback explains that the electron 'should lose energy at every turn and move closer and closer to the nucleus following a spiral path. The ultimate result is that it will fall into the nucleus...'

50. Rutherford's model could not explain which of the following phenomena?

Why the atom is mostly empty space. Why the atom has a positively charged nucleus. The stability of the atom and its line spectrum. The electrical neutrality of the atom.

Explanation: The 'Drawbacks' section is dedicated to explaining why the model fails to account for the stability of atoms and the nature of their observed, well-defined line spectra.