First applications of atomic theory


Through Robert M. Hazen, Ph.D., George Mason University

Atomic theory is one of the transformative ideas of all science. To get a historical idea of ​​the inexorable accumulation of evidence that has led to our modern acceptance of the idea of ​​the atom, let’s look at how the atomic theory hypothesis led to important scientific advances by Daniel Bernoulli and John Dalton .

The idea of ​​what constituted matter slowly evolved as scientific experiments developed. (Image: Dmitriy Rybin / Shutterstock)

Daniel Bernoulli

Swiss physicist Daniel Bernoulli lived in the middle of the 18th century, at the time of incredible discoveries in electricity, magnetism, etc. Daniel Bernoulli’s most famous work focused on the behavior of moving fluids, including the way air moved on a bird’s wing. He found that the air was moving faster over the curved upper surface of the wing than the lower surface, and this is what caused the lift. The upward pressure created lift, which explained how birds could fly.

In this context, he was studying atmospheric pressure and realized that if atoms were real, they must have mass. They must have speed and therefore kinetic energy.

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Volume, temperature and pressure

Bernoulli successfully applied Newton’s Second Law of Motion to this theoretical concept of atoms to explain the behavior of gases under pressure. For example, if you have doubled the number of gas particles, or if you have the volume of a container that contains a certain amount of gas, it doubles the number of collisions and it doubles the pressure on the containment walls.

A portrait of Daniel Bernoulli.
Daniel Bernoulli successfully applied Newton’s Second Law of Motion to the concept of atoms to explain the behavior of gases under pressure. (Image: Unknown / Public domain)

So, he measured pressure as a function of volume. For example, increasing the temperature increases the average kinetic energy in a very predictable way, and again you can see how the change in temperature changes the pressure inside a container.

You can also think about how a balloon behaves when you inflate it. It is easy to imagine individual particles flying inside the balloon pushing outward on its surface, even as the balloon elastic pushes inward on the particles. This creates a balancing force. It’s easier to think of it when you have the concept of atoms than if you just have an abstract continuum. This is how Bernoulli thought of it.

A key point here is that many of these observations do not prove that atoms exist. They just show that nature behaves as if atoms exist. And a lot of the first lines of evidence were like that.

Learn more about the nature of energy.

John dalton

A second important piece of evidence was put forward by the English meteorologist John Dalton, who lived from 1766 to 1844. It was Dalton who presented the first statement of atomic theory from a chemist’s point of view, and it was was in his three-volume treatise. called A new system of chemical philosophy. These volumes were published from 1808 to 1827.

Dalton was a poor country teacher. He gradually became known for his meteorological observations. He made meticulous studies of the weather. He was always curious, and he began to think about the nature of atoms through this study of time and how it varied from day to day, week to week, year to year. other, etc. He said:

Long accustomed to making meteorological observations and speculating on the nature and constitution of the atmosphere, I have often wondered how a compound atmosphere, or a mixture of two or more elastic fluids, could constitute a seemingly homogeneous mass.

What Dalton was saying is how can you take nitrogen and oxygen and other compounds and mix them together if they were kind of indivisible fluids? How were they going to mix? How were they going to combine? He couldn’t really imagine that.

Dalton’s determination

Dalton’s determined character, his willingness to understand nature, can be seen in the context of one of his best-known articles on color blindness. This work stems from a very embarrassing incident in Dalton’s life.

It turns out he was invited to join the austere Manchester Literary & Philosophical Society. And at one of his meetings, he showed up in a shining scarlet coat. Other members of society criticized him. “How could you come to this meeting with a shiny scarlet coat like that?” “

It was only then that Dalton learned he had red-green color blindness. And, this is how he began the first research which led to scientific publications on the phenomenon of this common variety of color blindness, which is now called color blindness.

Dalton’s atomic theory

A portrait of John Dalton.
Dalton’s atomic theory was developed at a time when chemists realized the law of definite proportions. (Image: Charles Turner / Public domain)

Dalton’s atomic theory states that matter is made up of atoms of perhaps several dozen different varieties. These are the different elements. These elements differ in their weight, size and properties.

He developed this theory at a time when the law of definite proportions in chemistry was first developing. This rule of thumb notes that if you take a given set of elements, they often combine with other elements in very specific proportions. For example, water is always eight parts oxygen to one part hydrogen atoms, and you always have that ratio.

Learn more about the nature of the materials.

The law of definite proportions

And if you look at other chemical compounds, you also see similar kinds of relationships developing over and over again, and you can see these patterns happening. Also, when two elements combine in more than one way, the weight ratio for the two compounds is going to be a simple whole number: 12 pounds of carbon can thus combine with 32 pounds of oxygen, or they can combine. with 64 lbs. oxygen.

So either 32 or 64, that’s a type of one-to-two ratio, simple ratios that popped up over and over again. This suggested to Dalton the reality of atoms because you combine units of substance into simple ratios.

However, many contemporaries still viewed atoms as just some kind of practical fiction, just a kind of nature-thinking that made calculations easier, but atoms weren’t necessarily real.

Common questions on the application of the atomic theory of Bernoulli and Dalton

Q: How did Bernoulli use atomic theory?

Bernoulli successfully applied Newton’s second law of motion. He applied them to the theoretical concept of atoms to explain the behavior of gases under pressure.

Q: How did Dalton view atomic theory?

Dalton presented the first statement of the atomic theory from a chemist’s point of view, in his three-volume treatise entitled A new system of chemical philosophy, published between 1808 and 1827.

Q: What does Dalton’s empirical theory of the elements note?

Dalton’s empirical law note that if you take a given set of items, they often combine with other items in very specific proportions.

Keep reading
Subatomic particles: the quantum realm
Contradictory thoughts on the first law of thermodynamics
Heat Theories: From Lavoisier to Earl Rumford and Sir Humphry Davy


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