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Who Was John Dalton? - Biography, Atomic Theory & Discovery

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  • 0:02 John Dalton Biography
  • 2:21 Atomic Theory
  • 5:36 Lesson Summary
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Lesson Transcript
Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

In this lesson, we will learn about John Dalton. We will learn about his life and how important learning and discovery was to him. We will also learn about his atomic theory and how it is important today.

John Dalton Biography

Ever since he was a child, John Dalton, 18th and 19th century English scientist, wanted to learn as much as possible, yet he was the son of a poor Quaker weaver. So, from a young age, he had to help provide for his family. But he didn't let this stop him from learning; he just found a way to do both. At the young age of twelve, he taught the local school. His eagerness to learn and his great understanding of math and science quickly moved him up in the ranks. By the time he was eighteen, he was the principal of a large school. This opened many other doors for him, such as being elected a member, and later the leader, of Manchester Literary and Philosophical Society. This society included access to a lab, which allowed him to start experimenting.

Dalton's first experiments had to do with meteorology. Throughout his entire life, he would watch the weather and track what was happening in order to better predict the weather. Dalton also early on began studying color blindness, because he and his brother both had this condition. Although all of his theories didn't prove completely accurate, he was the first to really study this disorder and he did discover that color blindness is hereditary. Due to his work, color blindness is now sometimes referred to as 'Daltonism'.

Dalton's study of weather included atmospheric pressure, which led him to study gases. His study of gases led to the discovery that gas and air are actually made up of molecules. They aren't just a chemical solvent, as had been previously believed. He also discovered what is known as Dalton's Law of Partial Pressures. This law is simply that the total pressure of a system is going to be equal to the partial pressures of each individual gas. This discovery led to one of his greatest discoveries: all matter is made up of individual particles called atoms. He developed this discovery into his atomic theory.

Dalton received many honors for the work he did. His Quaker upbringing, and the modesty encouraged in that practice, prompted him to resist public praise. But before his death, he received honorary doctorates from Oxford and Edinburgh University. In 1844, at the age of 77, Dalton died of a stroke. Today, the basic understanding of chemistry is still based on the theories Dalton discovered and explored.

Atomic Theory

Dalton's atomic theory consists of four main points:

  1. All matter is made of small particles called atoms. Atoms cannot be divided, created, or destroyed.
  2. All atoms of a certain element are identical in mass and properties but are always different from one element to the next.
  3. Compounds are formed by combining two or more different kinds of atoms; compounds can never be a half of a particular atom.
  4. The rearrangement of atoms is a chemical reaction.

Although parts of these points have been shown to be false, the overall theory is still the same basis we use for chemical reactions today. We have been able to divide an atom through nuclear fission. And we have discovered that the atom is made up of even smaller particles, called electrons, protons, and neutrons.

The first point is important because it shows all matter can be defined by specific characteristics based on the characteristics of the atoms of which it is made. And although it has been shown the atom can be divided, this point is important because it leads to the idea of chemical equilibrium. Chemical equilibrium is how chemical reactions are often determined. For example, by knowing that we start with eight molecules of oxygen, we know that somewhere in the finished products will still be eight molecules of oxygen. This is the same for every molecule in a reaction.

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