Correct Option
The correct option is A-2, B-1, C-4, D-3
Explanation
The understanding of atomic structure evolved through specific experiments that identified fundamental subatomic particles and the arrangement of mass within the atom. These discoveries laid the foundation for modern atomic theory.
Detailed Analysis
- A. J.J. Thomson (Discovery of Electron): In 1897, J.J. Thomson conducted experiments with cathode ray tubes and identified negatively charged particles, which were later named electrons. This discovery proved that atoms are divisible.
- B. E. Goldstein (Discovery of Canal Rays): In 1886, E. Goldstein discovered a new type of radiation in gas discharge tubes. These rays, known as canal rays, were positively charged and led to the eventual discovery of the proton.
- C. E. Rutherford (Discovery of Nucleus): In 1911, Ernest Rutherford performed the alpha-particle scattering experiment (Gold Foil Experiment). Based on the deflection of alpha particles, he concluded that the positive charge and most of the mass of an atom are concentrated in a dense central region called the nucleus.
- D. J. Chadwick (Discovery of Neutron): In 1932, James Chadwick bombarded beryllium with alpha particles and observed the emission of a neutral particle with a mass slightly higher than that of a proton. This particle was named the neutron.
Key Takeaway
J.J. Thomson discovered the electron; E. Goldstein discovered canal rays; Ernest Rutherford discovered the atomic nucleus; and James Chadwick discovered the neutron.