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Q1. Dalton’s model considered atom to be:
Dalton’s model considered the atom to be indivisible and indestructible. He proposed that atoms are the smallest particles of matter and cannot be divided further. This was a fundamental part of his atomic theory, which also stated that atoms of the same element are identical in mass and properties. Later discoveries showed that atoms are divisible.
Q2. Which particle has positive charge?
A proton has a positive charge (+1). It is one of the three main subatomic particles, along with electrons (negative charge) and neutrons (no charge). Protons are located in the nucleus of the atom. An alpha particle has a +2 charge, but the question asks for a particle that has positive charge; proton is the fundamental positively charged particle.
Q3. Electrically charged objects are formed due to:
Electrically charged objects are formed due to the transfer of charged particles (electrons). When electrons are transferred from one object to another, the object that gains electrons becomes negatively charged, and the one that loses electrons becomes positively charged. This is the basis of static electricity.
Q4. The study of which phenomenon first indicated that atoms are divisible?
The study of static electricity first indicated that atoms are divisible. When objects are rubbed together, they become electrically charged due to the transfer of electrons. This showed that atoms contain smaller charged particles, proving that atoms are not indivisible as Dalton had proposed.
Q5. The symbol for a proton is:
The symbol for a proton is p⁺. The ‘p’ stands for proton, and the ‘+’ indicates its positive charge. The electron is represented by e⁻, the neutron by n⁰, and the alpha particle by α (which is a helium nucleus with a +2 charge).
Q6. Electrons are located:
Electrons are located outside the nucleus. They revolve around the nucleus in various energy levels or shells. The nucleus contains protons and neutrons. In Thomson’s model, electrons were thought to be embedded in a positive sphere, but modern atomic theory places them outside the nucleus.
Q7. Rubbing a comb with dry hair makes it attract paper due to:
Rubbing a comb with dry hair makes it attract paper due to electrical charge. When the comb is rubbed, electrons are transferred from the hair to the comb, giving the comb a negative charge. This charged comb then attracts small pieces of paper through electrostatic attraction.
Q8. Which particle has negligible mass?
The electron has negligible mass (approximately 1/1836 of the mass of a proton). Its mass is about 9.11 × 10⁻³¹ kg, which is considered negligible compared to protons and neutrons. Alpha particles are much heavier, and protons and neutrons have significant mass.
Q9. Alpha particles are:
Alpha particles are doubly positively charged helium ions. They are helium nuclei consisting of two protons and two neutrons, giving them a charge of +2. They are emitted by radioactive materials and were used by Rutherford in his famous gold foil experiment.
Q10. Most α-particles in Rutherford’s experiment:
Most α-particles in Rutherford’s experiment passed straight through the gold foil. This observation led Rutherford to conclude that atoms are mostly empty space. A small number of α-particles were deflected or bounced back, indicating the presence of a small, dense, positively charged nucleus.
Q11. Which model could not explain later experimental results?
The Dalton model could not explain later experimental results. Dalton’s model considered atoms as indivisible spheres. However, later discoveries of subatomic particles (electrons, protons, neutrons) and experiments on static electricity and radioactivity proved that atoms are divisible and have internal structure.
Q12. The main purpose of Rutherford experiment was:
The main purpose of Rutherford’s experiment was to determine the arrangement of electrons within the atom. By bombarding gold foil with alpha particles, he wanted to understand how atoms were structured. The experiment led to the discovery of the nucleus and showed that electrons orbit around it.
Q13. Thomson’s model explained that atoms are:
Thomson’s model explained that atoms are electrically neutral. In his plum pudding model, he proposed that electrons are embedded in a sphere of positive charge. The total positive charge equals the total negative charge of the electrons, making the atom neutral overall.
Q14. The mass of an electron is considered:
The mass of an electron is considered negligible compared to the mass of a proton or neutron. It is approximately 1/1836 of the mass of a proton, making it the lightest of the three main subatomic particles. This is why the mass of an atom is almost entirely from its nucleus.
Q15. Dalton proposed that atoms are:
Dalton proposed that atoms are indivisible. He believed that atoms were the smallest particles of matter and could not be broken down further. This was a key postulate of his atomic theory. However, later discoveries showed that atoms can be divided into smaller particles.
Q16. Thomson’s model could not explain:
Thomson’s model could not explain the large deflection of α-particles observed in Rutherford’s gold foil experiment. According to Thomson’s plum pudding model, α-particles should have passed straight through with minimal deflection. The large deflections observed proved that the positive charge was concentrated in a tiny nucleus.
Q17. The charge of a proton is:
The charge of a proton is +1 (in units of elementary charge). The proton carries a positive charge that is equal in magnitude to the negative charge of an electron (-1). This positive charge is what determines the atomic number of an element.
Q18. Canal rays led to the discovery of:
Canal rays led to the discovery of the proton. Canal rays (also called anode rays) were observed in a discharge tube by E. Goldstein. The positively charged particles in these rays were later identified as protons. The electron was discovered by J.J. Thomson, and the neutron by James Chadwick.
Q19. The mass of a proton is approximately:
The mass of a proton is approximately 2000 times that of an electron. The actual mass of a proton is about 1.67 × 10⁻²⁷ kg, while the electron’s mass is about 9.11 × 10⁻³¹ kg. This makes the proton about 1836 times heavier than the electron.
Q20. Which scientist discovered the electron?
J.J. Thomson discovered the electron in 1897. He conducted experiments with cathode rays and showed that they were streams of negatively charged particles. He called these particles “corpuscles,” which were later named electrons. This was the first discovery of a subatomic particle.
Q21. Dalton’s atomic theory failed to explain:
Dalton’s atomic theory failed to explain the existence of sub-atomic particles (electrons, protons, and neutrons). Dalton proposed that atoms were indivisible. However, the discovery of electrons and protons showed that atoms have internal structure and can be divided into smaller particles.
Q22. Canal rays are:
Canal rays are positively charged rays that consist of positive ions. They are produced in a discharge tube when the gas is ionized and positive ions move towards the cathode. Goldstein discovered canal rays, which led to the discovery of the proton.
Q23. In Thomson’s model, electrons are:
In Thomson’s model (plum pudding model), electrons are embedded in a sphere of positive charge. The positive charge was spread throughout the sphere, and the electrons were like raisins in a pudding. This model explained the electrical neutrality of atoms.
Q24. Protons are located:
Protons are located in the nucleus of the atom. The nucleus is the tiny, dense, positively charged center of the atom that contains protons and neutrons. Electrons orbit around the nucleus in various energy levels or shells.
Q25. The α-particle scattering experiment is also called:
The α-particle scattering experiment is also called the gold foil experiment. Rutherford and his colleagues bombarded a thin gold foil with alpha particles and observed their deflection. This experiment led to the discovery of the atomic nucleus and the planetary model of the atom.
Q26. Rutherford wanted to know:
Rutherford wanted to know the arrangement of electrons in the atom. He designed the gold foil experiment to understand how electrons were distributed within the atom. The results of the experiment led to the discovery of the nucleus and a new model of atomic structure.
Q27. The target in Rutherford’s experiment was:
The target in Rutherford’s experiment was a very thin gold foil. Gold was chosen because it can be hammered into extremely thin sheets (as thin as 0.0001 mm). This thinness allowed alpha particles to pass through with minimal obstruction.
Q28. The mass of an α-particle is:
The mass of an α-particle is 4 u (unified atomic mass units). An alpha particle consists of two protons and two neutrons, so its mass is approximately 4 u. This is why it is much heavier than an electron (which has negligible mass) and a proton (which has 1 u mass).
Q29. Thomson’s model is also called:
Thomson’s model is also called the plum pudding model. In this model, the atom is imagined as a positively charged “pudding” with negatively charged “plums” (electrons) embedded in it. This model was proposed by J.J. Thomson in 1904.
Q30. Rutherford’s experiment proved that:
Rutherford’s experiment proved that the atom has a nucleus. The observation that some alpha particles were deflected at large angles or bounced back indicated the presence of a small, dense, positively charged nucleus at the center of the atom. This was a major breakthrough in understanding atomic structure.
Q31. The positive charge in Thomson’s model is:
In Thomson’s model, the positive charge is spread throughout the sphere of the atom. Unlike Rutherford’s model (where positive charge is concentrated in the nucleus), Thomson proposed that the positive charge was uniformly distributed in a sphere with electrons embedded in it.
Q32. An atom is divisible because it contains:
An atom is divisible because it contains charged particles (electrons, protons, and later neutrons were discovered). The presence of these subatomic particles proves that atoms are not indivisible as Dalton had proposed. The discovery of charged particles was one of the first indications of atomic divisibility.
Q33. Which scientist studied static electricity to understand atoms?
J.J. Thomson studied static electricity to understand atoms. He conducted experiments on cathode rays and static electricity, which led to the discovery of the electron. His work showed that atoms contain smaller, negatively charged particles.
Q34. J.J. Thomson discovered the electron in:
J.J. Thomson discovered the electron in 1897. He was studying cathode rays and found that they were streams of negatively charged particles. He called these particles “corpuscles.” This discovery was a major milestone in physics and chemistry.
Q35. An atom is electrically neutral because:
An atom is electrically neutral because the positive charges (protons) and negative charges (electrons) balance each other. The number of protons in an atom equals the number of electrons, making the net charge zero. Neutrons have no charge and do not affect the charge balance.
Q36. The symbol for an electron is:
The symbol for an electron is e⁻. The ‘e’ stands for electron, and the ‘-‘ indicates its negative charge. Protons are denoted by p⁺, neutrons by n⁰, and alpha particles by α. This standard notation is used throughout chemistry and physics.
Q37. Rutherford used which particles in his experiment?
Rutherford used alpha (α) particles in his gold foil experiment. Alpha particles are positively charged helium nuclei (He²⁺). They were used because they are heavy and have sufficient energy to penetrate thin foils, and their scattering patterns could be observed.
Q38. Electrons in Thomson’s model are compared to:
Electrons in Thomson’s model are compared to currants (or plums) in pudding. This is why the model is called the “plum pudding model.” The positive charge is like the pudding, and the electrons are the currants embedded in it. The idea was that the electrons were scattered throughout the positive sphere.
Q39. Gold foil was chosen because it:
Gold foil was chosen for Rutherford’s experiment because it can be made extremely thin (as thin as 0.0001 mm). Gold is highly malleable and can be hammered into very thin sheets without breaking. This thinness was essential for allowing alpha particles to pass through.
Q40. The proton’s mass is approximately how many times the electron?
The proton’s mass is approximately 2000 times the mass of the electron. More precisely, it is about 1836 times. This large mass difference means that almost all the mass of an atom is concentrated in the nucleus (protons and neutrons).
Q41. In Thomson’s model, the atom resembles:
In Thomson’s model, the atom resembles a Christmas pudding (or plum pudding). The positive charge is like the pudding, and the electrons are like the fruits embedded in it. This model was proposed before the discovery of the nucleus and is now known to be incorrect.
Q42. Thomson’s atomic model is also called:
Thomson’s atomic model is also called the plum pudding model. It was proposed by J.J. Thomson in 1904. The model suggests that the atom is a sphere of positive charge with electrons embedded in it, resembling a pudding with plums.
Q43. The charge of an electron is:
The charge of an electron is -1 (in units of elementary charge). This negative charge is equal in magnitude to the positive charge of a proton (+1). The charge of an electron was first measured by Robert Millikan in his oil drop experiment.
Q44. Electrons and protons balance in an atom to make it:
Electrons and protons balance in an atom to make it electrically neutral. The number of protons (positive charge) is equal to the number of electrons (negative charge) in a neutral atom. This balance is what makes atoms stable and electrically neutral.
Q45. The atom contains:
The atom contains electrons and protons (and also neutrons). Protons and neutrons are in the nucleus, while electrons orbit around the nucleus. The balance of protons and electrons determines the electrical charge of the atom.
Q46. Canal rays were discovered by:
Canal rays were discovered by E. Goldstein in 1886. He observed positively charged rays (canal rays) in a discharge tube, which led to the discovery of the proton. Goldstein’s work complemented J.J. Thomson’s discovery of the electron.
Q47. What question arises regarding atoms of different elements?
Regarding atoms of different elements, the question arises: what makes atoms of one element different from another? This fundamental question led to the understanding that atoms of different elements have different numbers of protons (atomic numbers) and different masses. This is what distinguishes one element from another.
Q48. Which scientist first proposed an atomic model?
John Dalton first proposed an atomic model (Dalton’s atomic model) in 1808. He proposed that atoms are indivisible and indestructible spheres. Thomson, Rutherford, and Bohr later proposed more refined models based on experimental evidence.
Q49. Most α-particles passed straight through because:
Most α-particles passed straight through the gold foil because the atom is mostly empty space. The small nucleus occupies only a tiny fraction of the atom’s volume. The electrons are also very light and do not significantly affect the path of heavy alpha particles.
Q50. E. Goldstein discovered canal rays in:
E. Goldstein discovered canal rays in 1886. He observed positively charged rays moving towards the cathode in a discharge tube. These rays were later identified as positive ions, leading to the discovery of the proton. This discovery was made before J.J. Thomson’s discovery of the electron in 1897.