Atomic Structure & Cathode Rays

This quiz covers the fundamental particles of an atom and the discovery of the electron through J.J. Thomson's cathode ray tube experiment.

Pages: 5 Questions per page: 10

Rate this quiz

☆ ☆ ☆ ☆ ☆

Avg: 0.00 ( 0 )

Score: 0 Page 1 / 5

1. According to the text, what are the necessary conditions for producing cathode rays in a discharge tube?

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

Explanation: The text states, 'J.J. Thomson observed that, when a high voltage is applied between the electrodes fitted in discharge tube, at a very low pressure, some invisible radiations are emitted from the cathode.'

2. Who does the document credit with coining the term 'atom'?

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

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

3. In the discharge tube experiment, what causes the faint green glow on the glass wall?

The heat from the high voltage The reaction of the gas with the glass The bombardment of the glass wall by the cathode rays A reflection from the cathode

Explanation: The text explains, 'Glowing is due to the bombardment of glass wall by the cathode rays.'

4. Why is an atom considered electrically neutral as a whole?

The number of protons equals the number of neutrons. It contains no charged particles. The number of protons equals the number of electrons. The positive charge of the nucleus is cancelled by the vacuum.

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

5. Based on the text, why does no electric current flow through the tube when the gas pressure is at 1 atm?

The voltage is too low at 1 atm. The vacuum pump is not active. Gases are poor conductors of electricity at that pressure. The electrodes are made of non-conductive material.

Explanation: The text notes that at 1 atm, no current flows, and 'This is because the gases are poor conductor of electricity.'

6. In the diagram of the discharge tube, from which electrode do the cathode rays originate?

The positive electrode (Anode) The negative electrode (Cathode) The vacuum pump inlet The glass tube itself

Explanation: The diagram shows the rays, labeled 'Cathode rays', originating from the electrode marked with a negative sign (—), which is the cathode.

7. What is the modern description of an electron's behavior, as contrasted with the 'solar system' model?

Electrons follow a fixed, predictable orbit around the nucleus. Electrons are large particles that move slowly. It is based on complex mathematics and it's impossible to know an electron's exact position and action simultaneously. The 'solar system' model is completely accurate for all scientific purposes.

Explanation: The introductory paragraph states the modern description is based on 'complex mathematics' and that it is 'impossible to know exactly where an electron is and what it is doing.'

8. What are cathode rays, according to the 'Origin of Cathode rays' section?

Beams of protons A type of light wave High-speed electrons emitted from the cathode Positively charged gas ions

Explanation: The text clarifies, 'Cathode rays are electrons emitted first from the cathode.'

9. Which of the following topics is NOT listed under the 'AIM' section of the document?

To introduce Fundamental particles To explain quantum mechanics in detail To introduce Thomson's and Rutherford Atomic model To introduce terms like atomic number, mass number and isotopes

Explanation: The 'AIM' section lists introducing fundamental particles, Thomson's/Rutherford's models, and terms like atomic number, but does not mention explaining quantum mechanics in detail.

10. According to Dalton's original concept described in the text, the atom was considered to be:

A particle composed of electrons and protons Infinitely divisible and destructible The fundamental particle of matter, indivisible and indestructible Electrically charged

Explanation: The text says, 'The atom is the fundamental particle of matter and considered to be indivisible and indestructible.'

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

They travel in straight lines with high speed. They cause ionization of the gas through which they pass. Their nature depends on the gas taken in the discharge tube. They produce a heating effect.

Explanation: Point x under 'Properties of Cathode rays' explicitly states: '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 discovered the presence of positive rays (also known as anode rays)?

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

Explanation: The text states in the section 'Discovery of proton - study of Anode rays': 'Goldstein discovered the presence of positive rays.'

13. What modification to the cathode was essential in the experiment to observe anode rays?

It was heated to a high temperature. It was coated with zinc sulphide. It was perforated (had holes). It was made of a specific metal like tungsten.

Explanation: The text describes the experiment: 'He performed experiment in which he took a perforated cathode...' The diagram also labels the 'Perforated cathode'.

14. How are anode rays (positive rays) formed in the discharge tube?

Electrons are emitted from the anode. Atoms of the gas lose electrons. Atoms of the gas gain electrons. The zinc sulphide coating emits them.

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

15. How does the speed of anode rays compare to that of cathode rays?

Their speed is much greater. Their speed is much less. Their speed is exactly the same. Their speed varies and can be greater or less.

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

16. The negatively charged material particles that make up cathode rays are called:

Protons Anode rays Electrons Neutrons

Explanation: Point iii under 'Properties of Cathode rays' states that 'the negatively charged material particles constituting the cathode rays are called electrons.'

17. Who is credited with the discovery of the proton by proving it exists in the nuclei of all atoms?

Goldstein Dr. A.O. Rajee Ernest Rutherford The text does not specify.

Explanation: The text states, '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 in the year 1917.'

18. What happens when cathode rays strike the surface of hard metals like tungsten?

They produce green fluorescence. They produce X-rays. They are absorbed completely. They form positive rays.

Explanation: According to property vi of cathode rays, 'They produce X-rays when they strike against the surface of hard metals like tungsten, molybdenum etc.'

19. In the experiment for producing anode rays, where is the fluorescence observed?

On the surface of the anode. On the glass wall behind the cathode. On the glass wall behind the anode. Inside the vacuum pump.

Explanation: The text describes that the rays passing 'through the hole in the cathode gives fluorescence on the opposite glass wall coated with zinc sulphide.' This wall is behind the cathode.

20. What is true about the charge-to-mass (e/m) ratio for cathode rays?

It is constant. It depends on the gas in the tube. It is less than the ratio for anode rays. It is not mentioned in the text.

Explanation: Property xi for cathode rays states: 'For each cathode rays, the ratio of charge (e) to mass (m) is constant.'

21. According to the text, who discovered the electron?

Ernest Rutherford J.J. Thomson Millikan Chadwick

Explanation: The text under 'Fundamental particles' states that the electron was 'discovered by the J.J. Thomson'. The summary table also lists J.J. Thomson as the discoverer of the electron.

22. Which experiment was used to determine the charge of an electron?

Gold foil experiment Cathode ray tube experiment Oil drop experiment Beryllium bombardment

Explanation: Under section 1) Electron, the first bullet point states, 'Charge: It was determined by Millikan by oil drop experiment'.

23. What is the charge of a proton as listed in the summary table?

-1.6022x10⁻¹⁹ C Zero 1.672x10⁻²⁷ kg 1.6022x10⁻¹⁹ C

Explanation: The table titled 'Properties of Electron, Proton and Neutron' lists the charge of a proton as 1.6022x10⁻¹⁹ C.

24. The document states that the neutron is heavier than the proton by what percentage?

0.18% 18.37% 1.5% 0.01%

Explanation: In section 3) Neutron, the text specifies that the neutron's mass 'is heavier than proton by 0.18%'.

25. Who is credited with the discovery of the neutron?

J.J. Thomson Ernest Rutherford Millikan Chadwick

Explanation: Both the main text for section 3) Neutron and the summary table state that the neutron was discovered by Chadwick.

26. Based on the table, where are protons and neutrons located?

Outside the nucleus In the nucleus In electron shells Protons are inside, neutrons are outside

Explanation: The last row of the summary table, labeled 'Location', indicates that both protons and neutrons are found 'In the nucleus'.

27. According to the text, the nature of anode rays depends on what factor?

The type of metal used for the cathode The voltage applied The gas taken in the discharge tube The temperature of the tube

Explanation: Point (iv) at the top of the page states, 'The nature of anode rays depends on the gas taken in the discharge tube.'

28. Which particle is described as the 'heaviest and least stable' among the elementary particles?

Electron Proton Neutron Anode ray particle

Explanation: The last bullet point under section 3) Neutron states, 'Among all the elementary particles neutron is the heaviest and least stable.'

29. What is the value given for the charge on one mole of electrons, also known as 1 faraday?

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

Explanation: In the section about the electron, a bullet point reads: 'Charge on one mole of electron is 96500 coulombs or 1 faraday.'

30. What is the mass of an electron as listed in the summary table?

1.672x10⁻²⁷ kg 9.109x10⁻²⁸ g 1.675x10⁻²⁷ kg 9.109x10⁻³¹ kg

Explanation: The summary table under the 'Electron' column and in the 'Mass' row shows the value 9.109x10⁻³¹ kg.

31. According to the text, what is Thomson's atomic model also known as?

The planetary model The nuclear model The watermelon or plum pudding model The billiard ball model

Explanation: The text states, '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.'

32. What was a major limitation of Thomson's atomic model as mentioned in the text?

It could not explain the existence of electrons. It failed to explain the results of Rutherford's scattering experiment. It was too complex to be understood. It did not account for the atom's overall neutral charge.

Explanation: The text explicitly states under 'Limitation', 'This model failed explain the results of scattering experiment of Rutherford and the stability of atom.'

33. In Rutherford's alpha-ray scattering experiment, what was the purpose of the zinc sulphide (ZnS) screen?

To generate the alpha particles To hold the gold foil in place To deflect the alpha particles To detect the alpha particles by producing a flash of light

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

34. What material was bombarded by alpha particles in Rutherford's experiment, as shown in the diagram?

Silver foil Gold foil Lead block Copper plate

Explanation: The text mentions that Rutherford bombarded thin foils of metals like gold, and the diagrams are specifically labeled 'Gold foil'.

35. What was the most common observation in Rutherford's scattering experiment?

Most of the alpha particles were deflected by large angles. All alpha particles were absorbed by the foil. A few alpha particles bounced straight back. Most of the alpha particles passed through the foil without any deflection.

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

36. What major conclusion was drawn from the observation that most alpha particles passed straight through the gold foil?

The atom is a solid, indivisible sphere. The atom's positive charge is spread out like a pudding. The atom is largely empty space. Electrons are located in a central nucleus.

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

37. In Thomson's model, how is the electrical neutrality of the atom explained?

The atom has no charged particles. There is a central nucleus that cancels out the charge of orbiting electrons. The embedded electrons are sufficient to neutralize the sphere of positive charge. The positive and negative charges are in separate, non-interacting layers.

Explanation: The text describes Thomson's model as having 'a number of embedded electrons in it and sufficient enough to neutralize the positive charge.'

38. What was the source of the fast-moving particles used in Rutherford's experiment?

A cathode ray tube A radioactive source in a lead block A particle accelerator The gold foil itself

Explanation: The text states that Rutherford used 'a beam of fast moving radioactive particles originated from a lead block.' The diagram also shows a 'Radioactive source'.

39. Which of these is NOT a component of the experimental setup for Rutherford's scattering experiment as depicted in the diagram?

Radioactive source Gold foil ZnS screen Magnetic field generator

Explanation: The diagram shows a radioactive source, a beam of alpha particles, a gold foil, and a circular ZnS screen, but there is no mention or depiction of a magnetic field generator.

40. Based on the text, Rutherford's model was developed as a result of what?

A theoretical thought experiment The α-ray scattering experiment Revising the plum pudding model mathematically Observations of chemical reactions

Explanation: The section on Rutherford's Atomic Model begins by stating, 'Rutherford performed α-ray scattering experiment in which he bombarded thin foils of metals...'

41. According to Rutherford's model, where is most of the mass of an atom concentrated?

In the electrons orbiting the center Evenly distributed throughout the atom In the extra nuclear part In the small, positively charged nucleus

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

42. Why is Rutherford's atomic model also known as the 'planetary model'?

Because it was discovered using a telescope Because electrons are as large as planets Because it has resemblances to the solar system Because atoms are only found on planets

Explanation: Point 5 in the text explicitly says, 'Rutherford's model has resemblances with solar system. Hence it's also known as planetary model of the atom.'

43. What is a major drawback of Rutherford's model according to Maxwell's electromagnetic theory?

It cannot explain why the nucleus is positive. It predicts that atoms should be unstable as electrons spiral into the nucleus. It suggests that atoms are not electrically neutral. It overestimates the size of the nucleus.

Explanation: The 'Drawbacks' section explains that an orbiting electron should continuously lose energy, '...and closer to the nucleus following a spiral path. The ultimate result is that it will fall into the nucleus thereby making the atom unstable.'

44. How does Rutherford's model account for the electrical neutrality of an atom?

The number of electrons is equal to the number of positive charges in the nucleus. The atom has no charged particles. The nucleus has no charge. The positive and negative charges are mixed together evenly.

Explanation: Point 4 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.'

45. Rutherford's model failed to explain the nature of atomic spectra. What kind of spectrum did the model predict versus what is actually observed?

Predicted a line spectrum, but a continuous spectrum is observed. Predicted a continuous spectrum, but a spectrum of well-defined lines is observed. Predicted no spectrum at all, but a line spectrum is observed. Predicted a band spectrum, but a continuous spectrum is observed.

Explanation: The second drawback states, 'If the electrons lose energy continuously, the spectrum is expected to be continuous but the actual observed spectrum consists of well-defined lines of definite frequencies.'

46. Based on the text, what part of the atom is responsible for its volume?

The nucleus The extra nuclear part The protons The empty space between atoms

Explanation: The last sentence of point 6 says, '...the extra nuclear part is responsible for its volume.'

47. What force holds the electrons in their orbits around the nucleus in Rutherford's model?

Gravitational forces Magnetic forces Strong nuclear forces Electrostatic forces of attraction

Explanation: At the end of point 4, the text mentions, 'Electrons and the nucleus are held together by electrostatic forces of attraction.'

48. What inference was made from the observation that a few alpha particles were deflected at large angles?

The atom is mostly empty space. The electrons are negatively charged. There is a heavy, positive charge concentrated at the center of the atom. The atom has no charge.

Explanation: The text explains the deflection of alpha particles with the line: 'Bcz there is heavy positive charge at the center of the atom which causes repulsions.'

49. According to the principles of Rutherford's model described in the text, what is the fundamental structure of an atom?

A solid, positively charged sphere with electrons embedded in it. A spherical and mostly hollow entity with a central nucleus. A particle with no internal structure. A collection of only electrons.

Explanation: Point 1 under 'According to Rutherford' states, 'Atom is spherical and mostly hollow with a lot of empty space in it,' and point 2 mentions a 'small positively charged part at its center known as nucleus.'

50. What is the ultimate consequence for an electron in orbit according to the drawbacks of Rutherford's model?

It gains energy and moves to a higher orbit. It maintains a stable orbit indefinitely. It stops moving and hovers in place. It will lose energy and fall into the nucleus.

Explanation: The first drawback states, 'The ultimate result is that it will fall into the nucleus thereby making the atom unstable.'