Question

question 1 of 20 : select the best answer for the question. 1. in the nineteenth century, what was known about atoms? a. the half-life of all atoms b. the exact structure of all atoms c. the atom determines the chemical property of an element. d. the number of atoms that exist in the world is increasing. mark for review (will be highlighted on the review page)

Explanation:

• Option A: Half - life concepts were not fully understood for all atoms in the 19th century, especially as radioactivity and related phenomena were still being explored.
• Option B: The exact structure of atoms (like the Bohr model or quantum - mechanical models) was not known in the 19th century. The plum - pudding model was a later 19th - early 20th century idea and was not the exact structure of all atoms.
• Option C: In the 19th century, the idea that the atom (specifically, the properties of atoms of an element) determines the chemical property of the element was established. For example, Dalton's atomic theory and the development of chemical stoichiometry relied on the idea that atoms of different elements have different chemical properties.
• Option D: Atoms are conserved in chemical reactions, and the idea that the number of atoms in the world is increasing is incorrect from a chemical perspective, and there was no basis for this idea in the 19th century.

Answer:

C. The atom determines the chemical property of an element.