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Assertion (A): The discovery of subatomic particles helped in understanding the atomic structure. Reason (R): The number of electrons is equal to the number of protons in an atom. Choose the correct option: (i) Both A and R are true and R is the correct explanation of A. (ii) Both A and R are true, but R is not the correct explanation of A. (iii) A is true, but R is false. (iv) A is false, but R is true.
Option (ii) is the correct choice. Assertion A is true because discovering electrons, protons and neutrons explained internal organization, chemical behavior and bonding. Reason R is also true because an atom contains equal counts of protons and electrons, ensuring neutrality. However, statement R sRead more
Option (ii) is the correct choice. Assertion A is true because discovering electrons, protons and neutrons explained internal organization, chemical behavior and bonding. Reason R is also true because an atom contains equal counts of protons and electrons, ensuring neutrality. However, statement R simply describes atomic electrical balance and does not serve as the complete scientific explanation for how subatomic discoveries unveiled overall atomic structure.
For more NCERT Solutions of Class 9 Science Exploration Chapter 8 Journey Inside the Atom Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-8/
See lessExplain and arrange the following statements in the correct chronological order to show how atomic models have evolved over time. (i) Bohr’s model proposed that electrons move in fixed orbits around the nucleus, each with a definite energy. (ii) Thomson’s model depicted the atom as a ‘plum pudding’ with electrons embedded in a sphere of positive charge. (iii) Rutherford’s model proposed that atoms have a dense central nucleus. (iv) Dalton’s model described atoms as indivisible particles.
The correct chronological sequence is (iv), (ii), (iii), then (i). In 1808, Dalton modeled atoms as indivisible building blocks. In 1897, Thomson proposed the plum pudding model featuring embedded electrons. In 1911, Rutherford established that atoms contain a dense positive central nucleus. FinallyRead more
The correct chronological sequence is (iv), (ii), (iii), then (i). In 1808, Dalton modeled atoms as indivisible building blocks. In 1897, Thomson proposed the plum pudding model featuring embedded electrons. In 1911, Rutherford established that atoms contain a dense positive central nucleus. Finally, in 1913, Bohr proposed that electrons revolve within stable, fixed energy shells without radiating energy.
For more NCERT Solutions of Class 9 Science Exploration Chapter 8 Journey Inside the Atom Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-8/
See lessElectrons move around the nucleus in orbits. Why do they not fly away from the atom? Explain what keeps them attracted to the nucleus.
Electrons remain bound within the atom because of the electrostatic force of attraction operating between opposite electric charges. The atomic nucleus contains positively charged protons, whereas the revolving electrons carry negative charges. This mutual electrical attraction pulls the electrons iRead more
Electrons remain bound within the atom because of the electrostatic force of attraction operating between opposite electric charges. The atomic nucleus contains positively charged protons, whereas the revolving electrons carry negative charges. This mutual electrical attraction pulls the electrons inward toward the nucleus, providing the required centripetal attraction that keeps them in their orbits and prevents them from flying away into space.
For more NCERT Solutions of Class 9 Science Exploration Chapter 8 Journey Inside the Atom Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-8/
See lessWhat conclusion did Rutherford draw about the position and characteristics of the atom’s positively charged part based on the few alpha particles that bounced back or were deflected at large angles in the gold foil experiment?
Rutherford concluded that the positive charge and nearly all the mass of the atom are concentrated in an extremely small, dense region located at the center, known as the nucleus. Because only a tiny fraction of positively charged alpha particles rebounded or suffered large deflections, this centralRead more
Rutherford concluded that the positive charge and nearly all the mass of the atom are concentrated in an extremely small, dense region located at the center, known as the nucleus. Because only a tiny fraction of positively charged alpha particles rebounded or suffered large deflections, this central nucleus must be very small compared to the total volume and intensely positively charged.
For more NCERT Solutions of Class 9 Science Exploration Chapter 8 Journey Inside the Atom Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-8/
See lessWhich of the following statements are correct or incorrect according to the Bohr’s atomic model? Give a reason for each statement. (i) Electrons lose energy while moving in fixed orbits and slowly fall into the nucleus. (ii) Electrons can exist anywhere around the nucleus with no fixed energy. (iii) Electrons revolve around the nucleus in orbits of fixed energy without losing energy. (iv) Electrons can be found between energy levels as they move around the nucleus.
Statement (iii) is correct because Bohr postulated that electrons revolve in designated orbits called stationary states where they do not radiate energy, maintaining atomic stability. Statement (i) is incorrect because non-radiating orbits prevent electrons from falling into the nucleus. StatementsRead more
Statement (iii) is correct because Bohr postulated that electrons revolve in designated orbits called stationary states where they do not radiate energy, maintaining atomic stability. Statement (i) is incorrect because non-radiating orbits prevent electrons from falling into the nucleus. Statements (ii) and (iv) are incorrect because electrons have strictly quantized energies and can only occupy specific allowed shells, never arbitrary spaces between them.
For more NCERT Solutions of Class 9 Science Exploration Chapter 8 Journey Inside the Atom Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-8/
See less