Gen Chem 1

John Dalton

Propesed the Theory of Atomic Law

(1766-1844)

Law of Conservation of Mass

Antoine Lavoisier (1754-1826)

 

In a chemical reaction, matter is neither created nor destroyed.

Total mass of the materials you have before the reaction must equal the total mass of the materials you have at the end.

Law of Definite Proportions

Joseph Proust (1754-1826)

 

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.

Law of Multiple Proportions

John Dalton (1766-1844)

 

When two elements (call them A and B) form two different
compounds, the masses of B that combine with 1 g of A can be expressed as:

  a ratio of small whole numbers.

Atomic Theory

John Dalton (1766-1844)

created 1808

 

1)Each element is composed of tiny, indestructible particles called atoms.
2)All atoms of a given element have the same mass and other properties that distinguish them from atoms of other elements.
3)Atoms combine in simple, whole-number ratios to form molecules of compounds.
4)In a chemical reaction, atoms of one element cannot change into atoms of another element.
They simply change the way they are attached!

Cathode Ray Tube Experiment

J J Thomsons Experiment
(late 1800’s)

Investigated the effect on a cathode ray by placing an electric field around a tube 

The cathode rays are made of tiny particles.

These particles have a negative charge.

because the beam always deflected toward the + plate

The amount of deflection was related to two factors, the charge and mass of the particles.

Every material tested contained these same particles.

The charge:mass ratio of these particles was

        −1.76 × 108

C/g.

 

 Oil Drop Experiment

Millikin (1909)

 

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