Law of Definite Proportion

A given compound always contains the same proportion by mass of its constituent elements.



The Law of Multiple Proportions

When two elements combine to form a series of compounds, the ratio of the mass of the second element which will combine with 1 gram of the first will always be reducible to a small whole number. (Similarly, with multi-element compounds {other than macromolecules}, the ratios of the elements also reduce to small whole numbers.)













Dalton's atomic theory

  1. All matter is composed of ultimately small particles, called atoms.

  2. Atoms are permanent and indivisible - they can neither be created nor destroyed.

  3. Elements are characterized by their atoms. All atoms of a given element are identical in all respects. Atoms of different elements have different properties.

  4. Chemical change consists of a combination, separation, or rearrangement of atoms.

  5. Chemical compounds are composed of atoms of two or more elements in fixed ratios.









hydrogen atom line spectra compared to a continuous spectra ("rainbow")













millikins oil drop apparatus

Image of Millikin's refined apparatus for the oil drop experiment (Millikin, 1917)

public domain image via Wikipedia




© R A Paselk

Last modified 30 January 2013