Illustration of Atomic theory

1808 Atomic theory

The book of science

Tom Sharp

John Dalton physics Illustration of Atomic theory

Atomic theory

invisible & irreducible atoms remained controversial since Democritus in the fifth century until John Dalton seeing that common chemical processes produced elements in fixed proportions— so much hydrogen per oxygen in water so much oxygen per carbon in carbon dioxide claimed that chemical elements are made of atoms atoms of the same element have the same weight atoms of different elements have different weights atoms combine in only small whole-number ratios to form molecules (which he called “compound atoms”) and atoms cannot be created or destroyed (by chemical processes).


hydrogen (a circle with a dot in the center) Describing atoms as spherical bodies, Dalton proposed a uniform notation for atoms and molecules —each a circle containing a letter or decoration. These circles formed an alphabet which chemists could use to spell more complex compounds. His circle for hydrogen contained a dot— same as the Egyptian hieroglyph for the sun, ‘ra,’ which had not yet been decyphered.


If an atom cannot be destroyed, then these are not atoms— lives, families, languages, tribes, happiness, peace of mind, faith, belief, hope. If I were to symbolize my love with a plus-sign and put that sign in a circle, then I would be trying to say my love cannot be destroyed.

Before we had atomic force microscopes, the existence of atoms and molecules had to be deduced from chemical experiments.

Dalton was the first to assemble the evidence into a complete theory, and the first to prepare a table of the atomic weights of known elements and molecules. As a poet, I am impressed that he invented an alphabet to symbolize the elements and molecules. These are more interesting and artistic than the two-letter chemical symbols based on the Greek that we use today.

My editorial insertion is the parenthetical “(by chemical processes)” in the list of Dalton’s claims, since we know now that an atom may be destroyed.

Around 1787, Dalton rediscovered George Hadley’s theory about trade winds. In 1801 he published a book on English grammar. Dalton suffered a less common form of color-blindness, deuteranopia, and was the first to describe and explain color blindness, proposing that it was due to a discoloration of the liquid medium of the eyeball, which was wrong. In his honor color blindness is sometimes called Daltonism, and the unit of atomic mass the dalton.

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