In which year did John Dalton propose his atomic theory?

• A. 1789
• B. 1905
• C. 1869
• D. 1808

Answer: (D)

Verified step by step guidance

1. Understand that John Dalton's atomic theory is a foundational concept in chemistry that introduced the idea that matter is composed of indivisible atoms.
2. Recall the historical timeline of scientific discoveries related to atomic theory, noting that Dalton's work predates the discovery of electrons and the periodic table.
3. Identify that Dalton proposed his atomic theory in the early 19th century, specifically in the year 1808.
4. Recognize that the other years listed (1789, 1869, 1905) correspond to different scientific milestones: 1789 relates to Lavoisier's work on elements, 1869 to Mendeleev's periodic table, and 1905 to Einstein's work on the photoelectric effect.
5. Conclude that the correct year for John Dalton's atomic theory proposal is 1808.