How do we know that matter consist of atom?

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Homework Help Overview

The discussion revolves around understanding the atomic theory and the evidence supporting the existence of atoms in matter. Participants explore historical perspectives and scientific principles related to atomic structure.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss Avogadro's Number and its relation to the number of atoms in a substance. There are references to historical figures like John Dalton and the development of atomic theory, including the significance of fixed proportions in chemical reactions.

Discussion Status

The discussion includes various interpretations of atomic theory and its historical context. Some participants provide insights into the evolution of the concept of atoms, while others question the relevance of certain terms like 'valency' in Dalton's rationale. There is an ongoing exploration of how these ideas developed over time.

Contextual Notes

Participants note the historical context of atomic theory, including the contributions of Dalton and the acceptance of atomic hypotheses among chemists and physicists. There is mention of the Karlsruhe congress and Jean Perrin's work, indicating the gradual acceptance of atomic theory in the scientific community.

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Homework Statement



How do we know that matter consist of atom?

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The Attempt at a Solution

 
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The number of atoms or molecules in a given amount of substance is related by Avogadro's Number. What ways exist of determining it?
 
If I remember correctly, it was John Dalton who first proposed the existence of atoms. Read up on how he came to that conclusion. The word 'valency' comes into it.
 
AJ Bentley said:
If I remember correctly, it was John Dalton who first proposed the existence of atoms. Read up on how he came to that conclusion. The word 'valency' comes into it.

(Well, if you discount the Greeks..) But valency doesn't come into Dalton's rationale, actually. (It wasn't a known concept during his lifetime, even.) Dalton had found the "law of fixed proportions"; that chemical elements appeared to react and combine in certain fixed proportions, which the atomic hypothesis explained.

But it wasn't until the Karlsruhe congress of 1860 that the hypothesis was generally accepted among chemists, (but not among contemporary physicists, notably Ernst Mach). It wasn't until Jean Perrin's 1913 book "Les Atomes" that the last die-hards were convinced.
 
alxm said:
But valency doesn't come into Dalton's rationale

He didn't use the word, granted. I was merely laying a crumb trail for the OP to follow.
 
Or look up STM images on google :)
 

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