Which of the following was the first subatomic particle to be discovered?

• A. Positron
• B. Neutron
• C. Proton
• D. Electron

Answer: (D)

Verified step by step guidance

1. Understand the historical timeline of subatomic particle discoveries to identify which particle was discovered first.
2. Recall that the electron was discovered by J.J. Thomson in 1897 through cathode ray tube experiments, marking the first identification of a subatomic particle.
3. Note that the proton was discovered later by Ernest Rutherford in 1917, identified as a positively charged particle within the nucleus.
4. Recognize that the neutron was discovered by James Chadwick in 1932, as a neutral particle in the nucleus.
5. Understand that the positron, the electron's antiparticle, was discovered even later in 1932 by Carl Anderson through cosmic ray experiments.