John Dalton Atom

Posted : admin On 1/29/2022

Although a schoolteacher, a meteorologist, and an expert on color blindness, John Dalton is best known for his pioneering theory of atomism.

He also developed methods to calculate atomic weights and structures and formulated the law of partial pressures.

  1. Many consider 2008 the 200th anniversary of atomic theory, John Dalton’s momentous theory of the nature of matter. Dalton (1766–1844) proposed that all matter in the universe is made of indestructible, unchangeable atoms—each type characterized by a constant mass—that undergo chemical reactions by joining with and separating from each other.
  2. 47 Dalton, John, ‘ Letter from Mr. Dalton, containing observations concerning the determination of the zero of heat, the thermometrical gradation, and the law by which dense or non-elastic fluids expand by heat ’, A Journal of Natural Philosophy, Chemistry, and the Arts (1803) 5, pp. 34 – 36 Google Scholar, 35.
  3. Dalton’s atomic theory proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass. Dalton’s atomic theory also stated that all compounds were composed of combinations of these atoms in defined ratios.
  4. The Solid Sphere Model was the first atomic model and was developed by John Dalton in the early 19th century. He hypothesized that an atom is a solid sphere that could not be divided into smaller particles. He came up with his theory as a result of his research into gases. He realized that certain gases only combined in specific proportions.

Early Life

John Dalton Atomic Theory Timeline

John Dalton Atom

Dalton (1766–1844) was born into a modest Quaker family in Cumberland, England, and for most of his life—beginning in his village school at the age of 12—earned his living as a teacher and public lecturer. After teaching for 10 years at a Quaker boarding school in Kendal, he moved on to a teaching position in the burgeoning city of Manchester. There he joined the Manchester Literary and Philosophical Society, which provided him with a stimulating intellectual environment and laboratory facilities. The first paper he delivered before the society was on color blindness, which afflicted him and is sometimes still called Daltonism.

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Modern Atomic Theory (John Dalton) Experiments with gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom based on the following assumptions. Matter is made up of atoms that are indivisible and indestructible. All atoms of an element are identical.

John Dalton, F.R.S., engraved by William Henry Worthington after an 1814 painting by William Allen, published June 25, 1823, in Manchester and London. Note the charts with Dalton’s atomic symbols lying on the table.

John Dalton Atom

Theories of Atomism and the Law of Partial Pressures

Dalton arrived at his view of atomism by way of meteorology, in which he was seriously interested for a long period: he kept daily weather records from 1787 until his death, his first book was Meteorological Observations (1793), and he read a series of papers on meteorological topics before the Literary and Philosophical Society between 1799 and 1801.

John Dalton Atomic Model

The papers contained Dalton’s independent statement of Charles’s law (see Joseph Louis Gay-Lussac): “all elastic fluids expand the same quantity by heat.” He also clarified what he had pointed out in Meteorological Observations—that the air is not a vast chemical solvent as Antoine-Laurent Lavoisier and his followers had thought, but a mechanical system, where the pressure exerted by each gas in a mixture is independent of the pressure exerted by the other gases, and where the total pressure is the sum of the pressures of each gas. In explaining the law of partial pressures to skeptical chemists of the day—including Humphry Davy—Dalton claimed that the forces of repulsion thought to cause pressure acted only between atoms of the same kind and that the atoms in a mixture were indeed different in weight and “complexity.”

Arnold Thackray describes how John Dalton's book on meteorology led to his discovery of the nature of atoms.


Experiments on Atomic Weights and Structures

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Elements and their combinations as described in John Dalton’s New System of Chemical Philosophy (1808–1827).

He proceeded to calculate atomic weights from percentage compositions of compounds, using an arbitrary system to determine the likely atomic structure of each compound. If there are two elements that can combine, their combinations will occur in a set sequence. The first compound will have one atom of A and one of B; the next, one atom of A and two atoms of B; the next, two atoms of A and one of B; and so on. Hence, water is HO. Dalton also came to believe that the particles in different gases had different volumes and surrounds of caloric, thus explaining why a mixture of gases—as in the atmosphere—would not simply layer out but was kept in constant motion. Dalton consolidated his theories in his New System of Chemical Philosophy(1808–1827).

As a Quaker, Dalton led a modest existence, although he received many honors later in life. In Manchester more than 40,000 people marched in his funeral procession.

Atomic Theory Explains That

Visit the Science History Institute to learn more about Dalton.

John Dalton Atomic Model

The information contained in this biography was last updated on December 4, 2017.