O Experimento da folha de ouro de Rutherford | Estrutura eletrônica de átomos |Química |Khan Academy

Summary

Ernest Rutherford's gold foil experiment transformed our understanding of atomic structure. By firing alpha particles at a thin gold foil, Rutherford observed unexpected deflections, leading to the discovery that atoms have a small, dense, positively charged nucleus. This finding challenged J.J. Thomson's 'plum pudding' model, and Rutherford's nuclear model, which posited that most of the atom is empty space with electrons orbiting a central nucleus, became foundational in atomic theory. The experiment paved the way for later developments in quantum mechanics and the modern understanding of atomic structure.

Takeaways

• 😀 Rutherford described an experiment that led to a groundbreaking discovery in atomic structure.
• 😀 He compared the unexpected results of his experiment to shooting a 15-inch projectile at a paper napkin and having it bounce back.
• 😀 Rutherford's interest in alpha particles (α) led him to use radium (Ra) to emit these particles for his experiment.
• 😀 The α particle is a helium nucleus (He²⁺), composed of two protons and two neutrons, without any electrons.
• 😀 Thomson's 'plum pudding' model proposed that atoms consisted of electrons in a 'soup' of positive charge.
• 😀 Rutherford's experiment involved directing alpha particles at a thin gold foil to probe the atomic structure.
• 😀 Most alpha particles passed straight through the gold foil, as Rutherford expected based on Thomson's model.
• 😀 However, about 1 in 20,000 alpha particles ricocheted back, which was an unexpected and puzzling result.
• 😀 Rutherford's conclusion from this surprising outcome was that the atom must have a small, dense, positively charged nucleus.
• 😀 The new model Rutherford proposed was the nuclear model, where most of the atom is empty space, with a tiny, positively charged nucleus at the center.
• 😀 The discovery of the small nucleus helped explain why some alpha particles were deflected or bounced back, while others passed through the atom.

Q & A

What was the most incredible event in Rutherford's life according to his quote?

Rutherford described the most incredible event as almost being as astonishing as firing a 15-inch projectile at a piece of paper and having it ricochet back and hit him. This was in reference to his gold foil experiment, where an unexpected outcome led to the discovery of the atomic nucleus.

What was Rutherford's main interest in studying alpha particles (α)?

Rutherford's main interest in studying alpha particles (α) was to understand the structure of the atom. Alpha particles are helium nuclei (two protons and two neutrons), and he used them in his experiments to probe atomic structure.

What is the modern understanding of an alpha particle, and how did Rutherford use it in his experiment?

An alpha particle is a helium nucleus, consisting of two protons and two neutrons, with a positive charge. Rutherford used alpha particles emitted from radium and directed them at a thin gold foil to investigate the structure of the atom.

How did J.J. Thomson's atomic model differ from Rutherford's atomic model?

J.J. Thomson's atomic model, known as the 'plum pudding model,' suggested that the atom was a sphere of positive charge with negatively charged electrons embedded within it. In contrast, Rutherford's model proposed that the atom consists of a tiny, dense, positively charged nucleus, with electrons surrounding it in mostly empty space.

What was Rutherford's expectation when he conducted the gold foil experiment?

Rutherford expected that most alpha particles would pass through the gold foil with little or no deflection, based on Thomson's model, which predicted that the atom was mostly empty space with a diffuse positive charge.

What unexpected result did Rutherford observe in his experiment?

Rutherford observed that, in addition to some alpha particles passing through the foil, about 1 in 20,000 particles were deflected at large angles or even bounced back, which was completely unexpected based on the prevailing atomic model at the time.

How did Rutherford interpret the phenomenon of alpha particles bouncing back during the gold foil experiment?

Rutherford concluded that the atom must contain a small, dense, positively charged nucleus. The alpha particles that were deflected or bounced back had collided with this dense nucleus, which had a strong positive charge that repelled the alpha particles.

What was Rutherford’s conclusion about the structure of the atom based on his experiment?

Rutherford concluded that the atom has a small, dense, positively charged nucleus at its center, with the electrons located in the surrounding space. The majority of the atom is empty space, which explains why most alpha particles passed through the gold foil without deflection.

How did Rutherford estimate the size of the atomic nucleus relative to the entire atom?

Rutherford estimated that the nucleus of the atom was extremely small, about 1/10,000th of the size of the entire atom. This was based on the way the alpha particles interacted with the atom during the gold foil experiment.

What key feature of Rutherford’s atomic model set it apart from earlier models?

The key feature of Rutherford's atomic model was the presence of a dense, positively charged nucleus at the center of the atom, which contrasted with earlier models that depicted the atom as a uniform, indivisible mass or a 'pudding' of positive charge with electrons scattered inside.