📘 Model Test Questions Class 9 Chemistry Test # 5 for Chapter # 2 (Atomic Structure)
Prepared by Inam Jazbi – Learn Chemistry
📘 Short Answer-Questions (SLO based)
Prepared by Inam Jazbi – Learn Chemistry
Q1.
Write down the names of sub atomic particles their masses in a.m.u with their unit charges. OR Write down 3 characteristics of each fundamental particles.
Q2.
Justify that Rutherford atomic model has defects? OR Write down 2 defects of Rutherford’s atomic model.
📘 Long Questions Answers Chapter # 2
Prepared by Inam Jazbi – Learn Chemistry
Q3.
Describe briefly the experiments which provide clue and evidences of electron, proton and neutron in an atom.
Q4.
Discuss Rutherford's gold metal foil (alpha particles scattering) experiment in the light of structure of atom & write down postulates of his atomic model.
Q5.
How are cathode rays produced? Discuss discharge tube experiment for the discovery of electrons with 4 properties of cathode rays.
Q6.
Discuss Canal ray experiment for the discovery of protons with 4 properties of positive rays.
📘 Interactive MCQs with Answers — Click to Reveal the Correct Answer
Test Yourself!
1. In an atom, number of protons and neutrons are added to obtain:
🟥 (a) Number of electrons
🟦 (b) Number of nucleons
🟩 (c) Atomic number
🟨 (d) Number of isotopes
✔ Correct Answer: 🟦 (b) Number of nucleons
Reason: The total number of protons and neutrons present in the nucleus is called the nucleon number or mass number.
Reason: The total number of protons and neutrons present in the nucleus is called the nucleon number or mass number.
2. If proton number is 19, electron configuration will be:
🟥 (a) 2, 8, 9
🟦 (b) 2, 8, 8, 1
🟩 (c) 2, 8, 1
🟨 (d) 2, 8, 3
✔ Correct Answer: 🟦 (b) 2, 8, 8, 1
Reason: A neutral atom has the same number of electrons as protons. Potassium has 19 electrons, distributed as 2, 8, 8, 1.
Reason: A neutral atom has the same number of electrons as protons. Potassium has 19 electrons, distributed as 2, 8, 8, 1.
3. If nucleon number of potassium is 39, number of neutrons will be:
🟥 (a) 39
🟦 (b) 19
🟩 (c) 20
🟨 (d) 29
✔ Correct Answer: 🟩 (c) 20
Reason: Number of neutrons = Nucleon number − Proton number = 39 − 19 = 20.
Reason: Number of neutrons = Nucleon number − Proton number = 39 − 19 = 20.
4. The isotope C-12 is present in abundance of:
🟥 (a) 96.9%
🟦 (b) 97.6%
🟩 (c) 98.8%
🟨 (d) 99.7%
✔ Correct Answer: 🟩 (c) 98.8%
Reason: Carbon-12 is the most abundant naturally occurring isotope of carbon, with an abundance of approximately 98.9%. Therefore, 98.8% is the closest given option.
Reason: Carbon-12 is the most abundant naturally occurring isotope of carbon, with an abundance of approximately 98.9%. Therefore, 98.8% is the closest given option.
5. Electronic configuration is distribution of:
🟥 (a) Proton
🟦 (b) Electron
🟩 (c) Positron
🟨 (d) Neutron
✔ Correct Answer: 🟦 (b) Electron
Reason: Electronic configuration describes the distribution of electrons in different shells and subshells around the nucleus.
Reason: Electronic configuration describes the distribution of electrons in different shells and subshells around the nucleus.
6. Which one of the following is most penetrating?
🟥 (a) Electron
🟦 (b) Proton
🟩 (c) Alpha particle
🟨 (d) Neutron
✔ Correct Answer: 🟨 (d) Neutron
Reason: Neutrons have high penetrating power because they have no electric charge and are not directly deflected by electric or magnetic fields.
Reason: Neutrons have high penetrating power because they have no electric charge and are not directly deflected by electric or magnetic fields.
7. How many subshells are present in an L shell?
🟥 (a) One
🟦 (b) Two
🟩 (c) Three
🟨 (d) Four
✔ Correct Answer: 🟦 (b) Two
Reason: The L shell has principal quantum number n = 2. Therefore, it contains two subshells: 2s and 2p.
Reason: The L shell has principal quantum number n = 2. Therefore, it contains two subshells: 2s and 2p.
8. de Broglie extended the wave-particle duality to electron in:
🟥 (a) 1920
🟦 (b) 1922
🟩 (c) 1923
🟨 (d) 1925
✔ Correct Answer: 🟨 (c) 1923
Reason: de Broglie proposed the matter-wave concept for particles such as electrons in the mid-1920s. Among the given options, 1925 is the intended answer.
Reason: de Broglie proposed the matter-wave concept for particles such as electrons in the mid-1920s. Among the given options, 1925 is the intended answer.
9. Name the material of the screen which was used in Rutherford's atomic model experiment:
🟥 (a) Aluminum foil
🟦 (b) Zinc sulphide
🟩 (c) Sodium sulphide
🟨 (d) Aluminum sulphide
✔ Correct Answer: 🟦 (b) Zinc sulphide
Reason: A zinc sulphide (ZnS) fluorescent screen was used to detect the flashes produced when alpha particles struck the screen.
Reason: A zinc sulphide (ZnS) fluorescent screen was used to detect the flashes produced when alpha particles struck the screen.
10. Which rays are used for sterilization of medical instruments?
🟥 (a) α-rays
🟦 (b) β-rays
🟩 (c) γ-rays
🟨 (d) X-rays
✔ Correct Answer: 🟩 (c) γ-rays
Reason: Gamma rays have very high penetrating power and are used to destroy microorganisms during the sterilization of medical instruments.
Reason: Gamma rays have very high penetrating power and are used to destroy microorganisms during the sterilization of medical instruments.
11. How many subshells are present in an M shell?
🟥 (a) One
🟦 (b) Two
🟩 (c) Three
🟨 (d) Four
✔ Correct Answer: 🟩 (c) Three
Reason: The M shell has principal quantum number n = 3. Therefore, it contains three subshells: 3s, 3p and 3d.
Reason: The M shell has principal quantum number n = 3. Therefore, it contains three subshells: 3s, 3p and 3d.
12. How many subshells are present in a K shell?
🟥 (a) One
🟦 (b) Two
🟩 (c) Three
🟨 (d) Four
✔ Correct Answer: 🟥 (a) One
Reason: The K shell has principal quantum number n = 1. Therefore, it contains only one subshell, 1s.
Reason: The K shell has principal quantum number n = 1. Therefore, it contains only one subshell, 1s.
13. How many subshells are present in an N shell?
🟥 (a) One
🟦 (b) Two
🟩 (c) Three
🟨 (d) Four
✔ Correct Answer: 🟨 (d) Four
Reason: The N shell has principal quantum number n = 4. Therefore, it contains four subshells: 4s, 4p, 4d and 4f.
Reason: The N shell has principal quantum number n = 4. Therefore, it contains four subshells: 4s, 4p, 4d and 4f.
14. The electronic configuration of chlorine is:
🟥 (a) K2, L8, M5
🟦 (b) K2, L8, M1
🟩 (c) K2, L8, M7
🟨 (d) K2, L8, M8
✔ Correct Answer: 🟩 (c) K2, L8, M7
Reason: Chlorine has atomic number 17, so a neutral chlorine atom has 17 electrons distributed as K2, L8 and M7.
Reason: Chlorine has atomic number 17, so a neutral chlorine atom has 17 electrons distributed as K2, L8 and M7.
15. Which particle is the lightest in the following?
🟥 (a) Electrons
🟦 (b) Proton
🟩 (c) Neutron
🟨 (d) α-particles
✔ Correct Answer: 🟥 (a) Electrons
Reason: The mass of an electron is about 1/1836 of the mass of a proton, making it much lighter than a proton, neutron or alpha particle.
Reason: The mass of an electron is about 1/1836 of the mass of a proton, making it much lighter than a proton, neutron or alpha particle.
16. Which particle is heavier than the others?
🟥 (a) Electrons
🟦 (b) α-particles
🟩 (c) Neutron
🟨 (d) Proton
✔ Correct Answer: 🟦 (b) α-particles
Reason: An alpha particle consists of two protons and two neutrons. Its mass is therefore approximately 4 atomic mass units, making it heavier than an electron, proton or neutron.
Reason: An alpha particle consists of two protons and two neutrons. Its mass is therefore approximately 4 atomic mass units, making it heavier than an electron, proton or neutron.
17. Which of the following elements has the electronic configuration 1s2, 2s2 2p6, 3s2 3p4?
🟥 (a) Sulphur
🟦 (b) Nitrogen
🟩 (c) Iron
🟨 (d) Chloride ion
✔ Correct Answer: 🟥 (a) Sulphur
Reason: The configuration contains 16 electrons. An element with atomic number 16 is sulphur (S).
Reason: The configuration contains 16 electrons. An element with atomic number 16 is sulphur (S).
18. Which of the following elements has the electronic configuration 1s2, 2s2 2p6, 3s2 3p6, 4s2?
🟥 (a) Calcium
🟦 (b) Chromium
🟩 (c) Potassium
🟨 (d) Argon
✔ Correct Answer: 🟥 (a) Calcium
Reason: The configuration contains 20 electrons. The element with atomic number 20 is calcium (Ca).
Reason: The configuration contains 20 electrons. The element with atomic number 20 is calcium (Ca).
19. Which of the following has the electronic configuration 1s2, 2s2 2p6?
🟥 (a) Sodium ion
🟦 (b) Oxide ion
🟩 (c) Nitride ion
🟨 (d) All of them
✔ Correct Answer: 🟨 (d) All of them
Reason: Na⁺ has 10 electrons, O²⁻ has 10 electrons, and N³⁻ has 10 electrons. Therefore, all three ions have the configuration 1s2, 2s2 2p6.
Reason: Na⁺ has 10 electrons, O²⁻ has 10 electrons, and N³⁻ has 10 electrons. Therefore, all three ions have the configuration 1s2, 2s2 2p6.
20. Cathode rays experiment shows the presence of:
🟥 (a) Electrons
🟦 (b) Protons
🟩 (c) Neutrons
🟨 (d) Nucleus
✔ Correct Answer: 🟥 (a) Electrons
Reason: J. J. Thomson's cathode ray experiments demonstrated that cathode rays consist of negatively charged particles called electrons.
Reason: J. J. Thomson's cathode ray experiments demonstrated that cathode rays consist of negatively charged particles called electrons.
21. The e/m ratio of cathode rays (electrons) is:
🟥 (a) 1.7588 × 1011 C/kg
🟦 (b) 1.7588 × 108 C/g
🟩 (c) Both of them
🟨 (d) None of the above
✔ Correct Answer: 🟩 (c) Both of them
Reason: The specific charge (e/m) of an electron is approximately 1.7588 × 1011 C/kg. Since 1 kg = 1000 g, this is equal to 1.7588 × 108 C/g. Therefore, both values are correct.
Reason: The specific charge (e/m) of an electron is approximately 1.7588 × 1011 C/kg. Since 1 kg = 1000 g, this is equal to 1.7588 × 108 C/g. Therefore, both values are correct.
22. Which particle has a mass of 1/1836 times that of hydrogen?
🟥 (a) Electrons
🟦 (b) Protons
🟩 (c) Neutrons
🟨 (d) Positron
✔ Correct Answer: 🟥 (a) Electrons
Reason: The mass of an electron is approximately 1/1836 of the mass of a hydrogen atom (approximately the mass of a proton).
Reason: The mass of an electron is approximately 1/1836 of the mass of a hydrogen atom (approximately the mass of a proton).
23. Which particle has a mass of 1836 times that of electron?
🟥 (a) β-particles
🟦 (b) Protons
🟩 (c) Neutrons
🟨 (d) Positron
✔ Correct Answer: 🟦 (b) Protons
Reason: The mass of a proton is approximately 1836 times the mass of an electron.
Reason: The mass of a proton is approximately 1836 times the mass of an electron.
24. The e/m ratio for positive (anode) rays is __________ of the nature of gas used.
🟥 (a) Dependent
🟦 (b) Independent
🟩 (c) None of the above
🟨 (d) All of the above
✔ Correct Answer: 🟥 (a) Dependent
Reason: Positive rays are produced from the gas present in the discharge tube. Different gases produce positive ions with different masses, so their e/m ratio depends on the nature of the gas used.
Reason: Positive rays are produced from the gas present in the discharge tube. Different gases produce positive ions with different masses, so their e/m ratio depends on the nature of the gas used.
25. The e/m ratio of cathode rays is always __________ anode rays.
🟥 (a) Less than
🟦 (b) Greater than
🟩 (c) Equal to
🟨 (d) None of the above
✔ Correct Answer: 🟦 (b) Greater than
Reason: Cathode rays consist of electrons, which have a very small mass. Positive ions in anode rays are much heavier, so the e/m ratio of cathode rays is much greater than that of anode rays.
Reason: Cathode rays consist of electrons, which have a very small mass. Positive ions in anode rays are much heavier, so the e/m ratio of cathode rays is much greater than that of anode rays.
26. These are helium nuclei with double positive charge and atomic mass of 4 amu:
🟥 (a) Alpha rays
🟦 (b) Beta-rays
🟩 (c) Gamma rays
🟨 (d) X-rays
✔ Correct Answer: 🟥 (a) Alpha rays
Reason: Alpha particles are helium nuclei (⁴₂He) containing two protons and two neutrons. They have a double positive charge (+2) and a mass of approximately 4 amu.
Reason: Alpha particles are helium nuclei (⁴₂He) containing two protons and two neutrons. They have a double positive charge (+2) and a mass of approximately 4 amu.
27. Alpha rays consist of:
🟥 (a) Stream of hydrogen
🟦 (b) Stream of neutron only
🟩 (c) Stream of electron only
🟨 (d) Stream of helium nuclei
✔ Correct Answer: 🟨 (d) Stream of helium nuclei
Reason: Alpha radiation consists of a stream of alpha particles, and each alpha particle is a helium nucleus containing two protons and two neutrons.
Reason: Alpha radiation consists of a stream of alpha particles, and each alpha particle is a helium nucleus containing two protons and two neutrons.
28. The fast-moving electrons like the cathode rays are called:
🟥 (a) Alpha rays
🟦 (b) Beta-rays
🟩 (c) Gamma rays
🟨 (d) X-rays
✔ Correct Answer: 🟦 (b) Beta-rays
Reason: Beta-minus radiation consists of high-speed electrons emitted from unstable atomic nuclei. Therefore, beta particles are fast-moving electrons.
Reason: Beta-minus radiation consists of high-speed electrons emitted from unstable atomic nuclei. Therefore, beta particles are fast-moving electrons.
29. Which rays are electromagnetic radiations traveling with the velocity of light?
🟥 (a) Alpha rays
🟦 (b) Beta-rays
🟩 (c) Gamma rays
🟨 (d) X-rays
✔ Correct Answer: 🟩 (c) Gamma rays
Reason: Gamma rays are electromagnetic radiations and travel through vacuum at the speed of light. Note: X-rays are also electromagnetic radiations and travel at the speed of light, so this question is technically ambiguous. Gamma rays are the intended textbook answer.
Reason: Gamma rays are electromagnetic radiations and travel through vacuum at the speed of light. Note: X-rays are also electromagnetic radiations and travel at the speed of light, so this question is technically ambiguous. Gamma rays are the intended textbook answer.
30. Rutherford's alpha particle scattering experiment showed for the first time that the atom has:
🟥 (a) Electrons
🟦 (b) Protons
🟩 (c) Neutrons
🟨 (d) A nucleus
✔ Correct Answer: 🟨 (d) A nucleus
Reason: Rutherford's alpha particle scattering experiment showed that most of the atom is empty space and that nearly all of its positive charge and mass are concentrated in a small, dense nucleus.
Reason: Rutherford's alpha particle scattering experiment showed that most of the atom is empty space and that nearly all of its positive charge and mass are concentrated in a small, dense nucleus.
31. The mass of electron is:
🟥 (a) 9.11 × 10−26 kg
🟦 (b) 9.11 × 10−24 g
🟩 (c) 9.11 × 10−27 g
🟨 (d) 9.11 × 10−31 kg
✔ Correct Answer: 🟨 (d) 9.11 × 10−31 kg
Reason: The mass of an electron is approximately 9.11 × 10−31 kg, or 9.11 × 10−28 g.
Reason: The mass of an electron is approximately 9.11 × 10−31 kg, or 9.11 × 10−28 g.
32. The mass of proton is:
🟥 (a) 1.67 × 10−22 g
🟦 (b) 1.67 × 10−23 g
🟩 (c) 1.67 × 10−27 g
🟨 (d) 1.67 × 10−24 g
✔ Correct Answer: 🟨 (d) 1.67 × 10−24 g
Reason: The mass of a proton is approximately 1.67 × 10−27 kg, which is equal to 1.67 × 10−24 g.
Reason: The mass of a proton is approximately 1.67 × 10−27 kg, which is equal to 1.67 × 10−24 g.
33. The charge on an electron is:
🟥 (a) 1.602 × 10−16 C
🟦 (b) 1.602 × 10−17 C
🟩 (c) 1.602 × 10−19 C
🟨 (d) 1.602 × 10−18 C
✔ Correct Answer: 🟩 (c) −1.602 × 10−19 C
Reason: An electron carries one unit of negative elementary charge. Its charge is −1.602 × 10−19 C. The options give the magnitude only, so (c) is the intended answer.
Reason: An electron carries one unit of negative elementary charge. Its charge is −1.602 × 10−19 C. The options give the magnitude only, so (c) is the intended answer.
34. Which order is correct for the masses of these particles?
🟥 (a) Electron < Proton < Neutron
🟦 (b) Proton < Electron < Neutron
🟩 (c) Neutron < Electron < Proton
🟨 (d) Proton < Neutron < Electron
✔ Correct Answer: 🟥 (a) Electron < Proton < Neutron
Reason: The electron has the smallest mass, the proton is heavier than the electron, and the neutron is slightly heavier than the proton.
Reason: The electron has the smallest mass, the proton is heavier than the electron, and the neutron is slightly heavier than the proton.
35. An alpha particle consists of:
🟥 (a) 2 protons and 1 neutron
🟦 (b) 2 electrons and 2 neutrons
🟩 (c) 2 protons and 2 neutrons
🟨 (d) 2 protons and 3 neutrons
✔ Correct Answer: 🟩 (c) 2 protons and 2 neutrons
Reason: An alpha particle is the nucleus of a helium-4 atom. It contains two protons and two neutrons and has a charge of +2.
Reason: An alpha particle is the nucleus of a helium-4 atom. It contains two protons and two neutrons and has a charge of +2.
36. The nucleus of an atom consists of:
🟥 (a) Electrons and protons
🟦 (b) Protons and α-particles
🟩 (c) Nucleons
🟨 (d) Electrons and neutrons
✔ Correct Answer: 🟩 (c) Nucleons
Reason: The nucleus contains protons and neutrons. Protons and neutrons are collectively called nucleons.
Reason: The nucleus contains protons and neutrons. Protons and neutrons are collectively called nucleons.