Contributions of Scientists to Chemistry
From ZuluNotes - Free Leaving Cert Notes
There are many scientists on your chemistry course, and you need to have some information on each of them.
Contents |
The Scientists
The Following is a list of scientists who contributed to discoveries regarding atomic structure:
The Greeks
The greeks first postulated on the existance of atoms. They said:
- Elements are basic substances from which other materials are made.
- That there were 4 elements: Earth, Wind, Fire and Water
Robert Boyle
- Roberet boyle can be identified in pictures by the massive wig he wore
- He said:
- Elements are substances which can't be broken down into simpler materials
- Compounds are combinations of elements
Humphry Davy
- Develped electrolysis.
- Isolated (through use of electrolysis:
- Potassium (k)
- Barium (Ba)
- Strontium (Sr)
- Calcium (Ca)
- Magnesium (Mg)
Henry Moseley
- Discovered positive charge on nucleus using X-Rays.
- Called this charge 'Atomic Number.'
- Defined an element as a substance whose atoms all have the same atomic number.
John Dobereiner
- Formulated the Law of Triads.
- Recognised that Lithium(Li) Sodium(Na) and Calcium(Ca) had similar properties and that the atomic weight of Potassium was half way between that of the other two elements.
John Newlands
- Formulated Law of Octaves
- Placed elements in order of atomic weight.
- Noticed the properties of elements repeated themselves every 8th element.
- Tried to force all elements into this pattern and left no room for undiscovered elements.
Dmitri Mendeleev
- Placed elements in order of atomic weight.
- Left Gaps.
- Placed Iodine before Tellurium because of their respective properties and not their weights.
John Dalton
- Provided indirect evidence for existance of atoms
- Said:
- Atoms are indivisible and indestructable.
- Atoms of an element are identical and have the same properties and mass.
- Atoms of different elements vary in mass.
- Compounds contain atoms of different elements combined.
William Crookes
- Studied Cathode Rays.
- Showed Cathode Rays travel in straight lines.
J.J Thompson
- Showed cathode rays were attracted by a positive charge and therefore were negatively charged.
- Proved that they were very light.
- Said that they were sub-atomic particles.
- Proposed the 'Plum Pudding' model of the atom
- Plum pudding model contained a centre of positive charge interspersed with negative electrons.
George Stoney
- Had anticipated the discovery of the electron and gave it its name.
Roberet Millikan
- Performed the Millikan oil drop experiment
- Created a negatively charged oil mist
