How Did Chemists of the Past Measure Elements for the Periodic Table

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In summary, chemists of the past used quality balances to measure weight, and a lot of guesswork. Dalton was the first to propose and publish a system of atomic weights, but he was right about some and wrong about other weights, as were those who followed immediately. Chasing the Molecule is a fascinating story of how the correct values gradually unfolded.
  • #1
scientifico
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Hello, how did chemists of the past know the weight of the elements to build up the periodic table without using new lab tecniques ?
Have they transformed all the elements into gases and used Avogadro's law to obtain a relative atomic mass ? And how did they it was an element and not a compost ?

Thank you
 
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  • #2
They used quality balances to measure weight, and a lot of guesswork.

Some composite substances were considered elements till they were proved to be not.
 
  • #3
Borek said:
They used quality balances to measure weight, and a lot of guesswork.
Yes but to compare atomic weight of two elements you must be sure you have the same number of particles in both elements, how did they solved this ?
 
  • #4
What exactly do you mean with "whithout using new lab techniques"?
 
  • #5
withou the possibility to calculate the number of particles in a mole
 
  • #6
You don't need that, equivalent masses are relative.
 
  • #7
Borek said:
You don't need that, equivalent masses are relative.
What do you mean?
If I take 1 g of Fe and 1g of S I can't calculate relative atomic weight because they don't contains the same quantity of atoms...
 
  • #9
Dalton was the first to propose and publish a system of atomic weights.

Google "Dalton atomic weights" finds lots.

However he was right about some and wrong about other weights, as were those who followed immediately.

The story of how the correct values gradually unfolded is quite fascinating and well presented in the book

"Chasing the Molecule" by Julian Buckingham
 
  • #10
You don't need to have vapours. You can also infer the amount of moles e.g. from freezing point depression of solutions of salts, boiling point increase etc.
As others pointed out before, a lot can be learned from studying the mass proportions in different compounds.
 
  • #11
DrDu said:
You can also infer the amount of moles e.g. from freezing point depression of solutions of salts, boiling point increase etc.
What are that ?
 
  • #12
scientifico said:
What are that ?

Have you tried to google them or do you expect to be spoon feed all the time?
 

1. How did chemists of the past determine the atomic mass of elements?

Chemists of the past used a variety of methods to determine the atomic mass of elements. One of the earliest methods was through chemical reactions, where the mass of an element was compared to the mass of a known substance. Later on, more accurate techniques such as gravimetric analysis and mass spectrometry were developed.

2. How did chemists of the past classify elements into groups for the periodic table?

The classification of elements into groups for the periodic table was based on their chemical and physical properties. Chemists observed patterns among elements and organized them into groups based on their similar properties. This led to the development of the modern periodic table.

3. How did chemists of the past measure the atomic radius of elements?

The atomic radius of elements was measured using techniques such as X-ray crystallography, which involved analyzing the diffraction patterns of X-rays passing through a crystal of the element. Other methods included spectroscopy and electron microscopy.

4. How did chemists of the past determine the number of protons and electrons in an element?

The discovery of subatomic particles, such as protons and electrons, allowed chemists to determine the number of these particles in an element. This was done through experiments such as the cathode ray tube experiment and the gold foil experiment, which led to the understanding of the structure of atoms.

5. How did chemists of the past name newly discovered elements for the periodic table?

Newly discovered elements were often named after their properties, geographical location, or the scientists who discovered them. For example, helium was named after the Greek god of the sun, Helios, due to its presence in the sun's atmosphere. However, there were also controversies and disputes over the naming of elements, leading to changes in their names over time.

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