Who was the first to propose the existence of atoms?

• A. Ernest Rutherford
• B. J.J. Thomson
• C. John Dalton
• D. Democritus

Answer: (D)

Verified step by step guidance

1. Understand that the question is about the historical origin of the atomic theory, not a chemical calculation.
2. Recall that the concept of atoms as indivisible particles was first proposed in ancient times, long before modern chemistry developed.
3. Identify that Democritus, a Greek philosopher, was the first to suggest the existence of atoms around 400 BCE, describing them as tiny, indivisible particles that make up matter.
4. Recognize that John Dalton later developed the modern atomic theory in the early 19th century, providing experimental evidence and a scientific framework for atoms.
5. Note that Ernest Rutherford and J.J. Thomson contributed to atomic structure understanding but did not propose the original idea of atoms.