Atomic Models
16 Questions
5 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the approximate radius of an atom according to J.J. Thomson's model?

  • 10^(-8) m
  • 10^(-5) m
  • 10^(-12) m
  • 10^(-10) m (correct)

What is the shape of an atom according to J.J. Thomson's model?

  • Oval
  • Spherical (correct)
  • Cylindrical
  • Elliptical

What is the distribution of positive charge in an atom according to J.J. Thomson's model?

  • Concentrated at the center
  • Randomly distributed
  • Concentrated at the edges
  • Uniformly distributed (correct)

What is the mass of an atom assumed to be in J.J. Thomson's model?

<p>Uniformly distributed (B)</p> Signup and view all the answers

What did J.J. Thomson win the Nobel Prize for in 1906?

<p>Theoretical and experimental investigations on the conduction of electricity by gases (A)</p> Signup and view all the answers

What was the outcome of Rutherford's alpha-particle scattering experiment?

<p>Most alpha particles passed through the gold foil undeflected (C)</p> Signup and view all the answers

What was the purpose of the zinc sulphide screen in Rutherford's experiment?

<p>To produce a flash of light when alpha particles struck it (B)</p> Signup and view all the answers

What was the expectation of alpha particles passing through the gold foil according to Thomson's model?

<p>They would slow down and change direction by small angles (D)</p> Signup and view all the answers

What was the observation that led Rutherford to conclude that the positive charge of the atom is not spread throughout the atom?

<p>A few α–particles bounced back, deflected by nearly 180°. (C)</p> Signup and view all the answers

What is the ratio of the radius of the nucleus to the radius of the atom?

<p>10^(-5) (A)</p> Signup and view all the answers

What is the force that holds the electrons and the nucleus together?

<p>Electrostatic force of attraction (B)</p> Signup and view all the answers

What is the name given to the very small region of the atom where the positive charge and most of the mass are concentrated?

<p>Nucleus (D)</p> Signup and view all the answers

What is the shape of the paths in which electrons move around the nucleus?

<p>Circular (D)</p> Signup and view all the answers

What was the model proposed by Rutherford to describe the structure of the atom?

<p>Nuclear model (A)</p> Signup and view all the answers

What is the approximate size of the radius of the atom compared to a cricket ball representing the nucleus?

<p>5 km (A)</p> Signup and view all the answers

What was the observation that led Rutherford to conclude that most of the space in the atom is empty?

<p>Most of the α–particles passed through the foil undeflected. (A)</p> Signup and view all the answers

Flashcards

Approximate radius of an atom

10^(-10) m according to J.J. Thomson's model.

Shape of an atom (Thomson's model)

Atoms are modeled as spherical in shape.

Distribution of positive charge (Thomson's model)

Positive charge is uniformly distributed throughout the atom.

Mass of an atom (Thomson's model)

Mass is also considered uniformly distributed in the atom.

Signup and view all the flashcards

Nobel Prize of J.J. Thomson (1906)

For investigations on electricity conduction by gases.

Signup and view all the flashcards

Rutherford's alpha-particle experiment outcome

Most alpha particles passed through gold foil undeflected.

Signup and view all the flashcards

Zinc sulphide screen purpose

Produces a flash of light when struck by alpha particles.

Signup and view all the flashcards

Expectation vs. Observation (Thomson's model)

Expected alpha particles to slow down and change direction only slightly.

Signup and view all the flashcards

Rutherford's conclusion on positive charge

Surprising bounce-backs indicated positive charge is not spread out.

Signup and view all the flashcards

Nucleus size relation

The nucleus radius is about 10^(-5) times that of the atom.

Signup and view all the flashcards

Holding force between electron and nucleus

Electrostatic force of attraction keeps electrons near nucleus.

Signup and view all the flashcards

Region of atom with mass concentration

The nucleus is where positive charge and most mass are concentrated.

Signup and view all the flashcards

Electron paths around nucleus

Electrons move in circular paths around the nucleus.

Signup and view all the flashcards

Rutherford's atomic structure model

Proposed the nuclear model of the atom.

Signup and view all the flashcards

Size of atom vs. nucleus analogy

Radius of atom compared to a 5 km cricket ball-sized nucleus.

Signup and view all the flashcards

Space in atom (Rutherford's observation)

Most α–particles passed through foil, indicating atom is mostly empty space.

Signup and view all the flashcards

Study Notes

Thomson's Model of the Atom

  • In 1898, J.J. Thomson proposed a spherical atom model with a uniformly distributed positive charge (radius approximately 10^(-10) m).
  • Electrons are embedded in the sphere to create a stable electrostatic arrangement.
  • The model is also known as the plum pudding, raisin pudding, or watermelon model.

Rutherford's Experiment

  • Rutherford, Geiger, and Marsden bombarded thin gold foil with alpha particles in 1909.
  • A stream of high-energy alpha particles from a radioactive source was directed at a thin gold foil (thickness ~ 100 nm).
  • The results of the scattering experiment were unexpected:
    • Most alpha particles passed through the gold foil undeflected.
    • A small fraction of alpha particles was deflected by small angles.
    • A very few alpha particles (~ 1 in 20,000) bounced back, deflected by nearly 180°.

Rutherford's Conclusions

  • Most of the space in the atom is empty, as most alpha particles passed through the foil undeflected.
  • The positive charge of the atom is concentrated in a very small volume, which repelled and deflected positively charged alpha particles.
  • The volume occupied by the nucleus is negligibly small compared to the total volume of the atom.

Rutherford's Nuclear Model of the Atom

  • The positive charge and most of the mass of the atom are densely concentrated in an extremely small region called the nucleus.
  • The nucleus is surrounded by electrons that move around it with high speed in circular paths called orbits.
  • Electrons and the nucleus are held together by electrostatic forces of attraction.
  • The nucleus plays the role of the sun, and the electrons revolve around it like planets in the solar system.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser