Modelo Atômico de Thomson | Modelo Pudim de Passas | Atomística | Química Geral

Summary

This video explores the evolution of atomic models, focusing on Thomson's atomic model, which challenged Dalton's indivisible atom. Through experiments using cathode ray tubes, Thomson discovered that atoms are divisible and contain subatomic particles, such as electrons. His observations led to the understanding that atoms have a positive mass with negatively charged electrons distributed within them. This model, often referred to as the 'plum pudding' model, marked the discovery of the electron and revolutionized atomic theory. The video also covers important aspects of Thomson's findings, including the relationship between an electron's mass and charge.

Takeaways

• 😀 Thomson's atomic model differed from Dalton's, as Thomson conducted laboratory experiments rather than relying on imagination.
• 😀 Thomson's experiment involved cathode ray tubes, which showed that the rays traveled in a straight line regardless of the gas inside.
• 😀 The constant behavior of the rays suggested that atoms were divisible, which contradicted Dalton's theory of indivisible atoms.
• 😀 Thomson used charged plates to observe how the cathode rays were deflected, confirming that the rays were negatively charged.
• 😀 The discovery of the electron came from Thomson’s experiments with cathode rays, making it the first subatomic particle to be identified.
• 😀 Thomson’s model of the atom depicted a positively charged sphere with electrons distributed throughout, known as the 'plum pudding' model.
• 😀 The plum pudding model compares the atom to a cake with a positive mass (the dough) and electrons (the fruit) distributed throughout.
• 😀 Thomson's discovery of the electron was crucial, as it showed that atoms were not indivisible as previously thought.
• 😀 The key findings from Thomson's experiments include the divisibility of atoms and the existence of electrons as subatomic particles.
• 😀 Thomson's work with cathode rays helped establish the electron’s charge-to-mass ratio, a major milestone in atomic theory.

Q & A

What is the main difference between Dalton's and Thomson's atomic models?

Dalton's atomic model suggested that matter is made up of indivisible spheres, while Thomson's model, based on experimental observations, proposed that atoms are divisible and contain subatomic particles like electrons.

What was the key experimental tool used by Thomson in his research?

Thomson used cathode ray tubes in his experiments to study the behavior of gases at low pressures and investigate the properties of atoms.

Why are cathode ray tubes important in Thomson's discovery?

Cathode ray tubes allowed Thomson to observe the path of a beam of light, which led to the discovery that atoms contain negatively charged particles (electrons) and that atoms themselves are divisible.

What is the significance of the term 'rarefied gas' in Thomson's experiments?

A rarefied gas refers to a gas at low pressure, where there are fewer gas molecules. This allowed Thomson to observe the conduction of electricity, which otherwise would not have been possible with normal atmospheric gases.

What did Thomson discover about the charge of the particles in the cathode rays?

Thomson concluded that the particles in the cathode rays were negatively charged because they were attracted to the positive pole of an electric field.

What is the 'pudding model' of the atom as proposed by Thomson?

Thomson's 'pudding model' suggested that the atom is a positively charged sphere with electrons embedded within it, similar to fruit distributed in a cake (like raisins in a pudding or panettone).

How did Thomson's model challenge earlier ideas about the atom?

Thomson's model challenged the earlier idea, proposed by Dalton, that atoms were indivisible. He showed that atoms could be divided into smaller subatomic particles, specifically electrons.

What was the first subatomic particle to be discovered and by whom?

The first subatomic particle to be discovered was the electron, and it was discovered by J.J. Thomson through his experiments with cathode rays.

What does it mean that the atom is divisible according to Thomson's model?

According to Thomson's model, the atom is divisible because it contains smaller particles, such as electrons, within it, which could be separated and studied.

How does Thomson's model differ from the concept of indivisibility of matter proposed by earlier scientists?

Thomson's model contradicted earlier theories, such as those by Democritus, Leucippus, and Dalton, who proposed that atoms were indivisible. Thomson demonstrated that atoms are not the smallest unit of matter, as they are made up of even smaller particles (electrons).