NCERT Solutions for Class 9 Science Chapter 4
Structure of the Atom
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-49
Questions No-2
On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?
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On the basis of Rutherford’s model of an atom, protons (positively-charged particles) are present
in the nucleus of an atom.
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Rutherford’s Model and Subatomic Particles in the Nucleus:
– Model Overview: Rutherford proposed his atomic model after conducting the gold foil experiment. He observed that while most alpha particles passed through the foil, some were deflected, and a few bounced back, suggesting a concentrated, positively charged center termed the nucleus.
– Nucleus Composition:
– Rutherford’s model proposed that the nucleus, at the atom’s center, contains positively charged particles called protons.
– Nuclear Charge:
– Protons contribute to the atom’s positive charge and are concentrated within the small, dense nucleus.
– Gold Foil Experiment:
– This experiment showcased that a significant portion of the atom’s mass and positive charge is concentrated in the nucleus.
– Electron Surrounding:
– Electrons, negatively charged particles, were postulated to orbit the nucleus at a considerable distance, occupying most of the atom’s volume.
– Characteristics of the Nucleus:
– The nucleus, housing protons, constitutes a tiny fraction of the atom’s volume but contains most of its mass and positive charge.
Summary:
Rutherford’s model of the atom highlighted that the nucleus, located at the center, comprises positively charged particles known as protons. These protons are concentrated within the nucleus and contribute significantly to the atom’s positive charge and mass. This model revolutionized atomic theory, providing insights into the structure of the atom. Later discoveries revealed the presence of neutrons alongside protons in the nucleus, further enhancing our understanding of atomic composition.