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Questions and Answers
What did Rutherford conclude must exist in the center of the atom based on his experiments with alpha particles?
What did Rutherford conclude must exist in the center of the atom based on his experiments with alpha particles?
- A concentrated positive charge (correct)
- An electron cloud
- High energy levels
- A concentrated negative charge
What observation was made regarding most alpha particles during Rutherford's experiment?
What observation was made regarding most alpha particles during Rutherford's experiment?
- They passed straight through the foil. (correct)
- They produced high-energy reactions.
- They were absorbed by the foil.
- They all deflected back to the source.
What was the unexpected outcome of Rutherford's experiments with alpha particles?
What was the unexpected outcome of Rutherford's experiments with alpha particles?
- Most particles were absorbed by the foil.
- Most particles passed through the foil. (correct)
- All particles were deflected at the same angle.
- Particles created new elements upon collision.
Which model of the atom did Rutherford's results challenge?
Which model of the atom did Rutherford's results challenge?
What did Rutherford predict about the size of the positive charge relative to the entire atom?
What did Rutherford predict about the size of the positive charge relative to the entire atom?
What is one possible explanation for the deflection of alpha particles in Rutherford's experiment?
What is one possible explanation for the deflection of alpha particles in Rutherford's experiment?
What percentage of alpha particles were reflected back toward the source in Rutherford's experiment?
What percentage of alpha particles were reflected back toward the source in Rutherford's experiment?
What did the alpha particle bombardment of gold foil reveal about atomic structure?
What did the alpha particle bombardment of gold foil reveal about atomic structure?
What key idea do the quantum mechanical model and Heisenberg's uncertainty principle share?
What key idea do the quantum mechanical model and Heisenberg's uncertainty principle share?
According to the quantum mechanical model, how are orbitals described?
According to the quantum mechanical model, how are orbitals described?
Who first proposed the idea that electrons possess both particle and wave characteristics?
Who first proposed the idea that electrons possess both particle and wave characteristics?
What does the wave function represent in quantum mechanics?
What does the wave function represent in quantum mechanics?
How can electrons move between different orbitals according to the quantum mechanical model?
How can electrons move between different orbitals according to the quantum mechanical model?
In which state does the single electron in a hydrogen atom typically reside?
In which state does the single electron in a hydrogen atom typically reside?
What aspect of the quantum mechanical model makes it a complex understanding of atomic structure?
What aspect of the quantum mechanical model makes it a complex understanding of atomic structure?
What does electron probability density indicate?
What does electron probability density indicate?
What major contribution did Antoine Lavoisier make in the late 1700s?
What major contribution did Antoine Lavoisier make in the late 1700s?
According to John Dalton's atomic theory, what can be said about atoms of the same element?
According to John Dalton's atomic theory, what can be said about atoms of the same element?
What experimental evidence first supported the existence of the electron?
What experimental evidence first supported the existence of the electron?
What characteristic describes the cathode ray in J.J. Thomson's experiments?
What characteristic describes the cathode ray in J.J. Thomson's experiments?
Which scientific development allowed for the precise measurement of mass and volume in experiments?
Which scientific development allowed for the precise measurement of mass and volume in experiments?
How has John Dalton's atomic theory been viewed over time?
How has John Dalton's atomic theory been viewed over time?
What did J.J. Thomson refer to the apparatus he used in his experiments?
What did J.J. Thomson refer to the apparatus he used in his experiments?
What role did electrical discharges play in Thomson's experiments?
What role did electrical discharges play in Thomson's experiments?
What type of particles did Thomson hypothesize was in the cathode ray based on his observations?
What type of particles did Thomson hypothesize was in the cathode ray based on his observations?
What happens to the cathode ray in the presence of a negative electrical field?
What happens to the cathode ray in the presence of a negative electrical field?
Using which formula did Thomson determine the charge-to-mass ratio of an electron?
Using which formula did Thomson determine the charge-to-mass ratio of an electron?
In a cathode ray tube, which component is responsible for producing the visible ray under high voltage?
In a cathode ray tube, which component is responsible for producing the visible ray under high voltage?
What is the charge of the particles that compose the cathode ray according to Thomson’s hypothesis?
What is the charge of the particles that compose the cathode ray according to Thomson’s hypothesis?
What type of environment is required in a cathode ray tube for visualization of the cathode ray?
What type of environment is required in a cathode ray tube for visualization of the cathode ray?
What role does the metal electrode play in the cathode ray tube?
What role does the metal electrode play in the cathode ray tube?
Why did Thomson measure the deflection of the beam of electrons in a magnetic field?
Why did Thomson measure the deflection of the beam of electrons in a magnetic field?
What was one of Thomson's main goals in his cathode ray tube experiments?
What was one of Thomson's main goals in his cathode ray tube experiments?
Which model is often referred to as the 'blueberry muffin model'?
Which model is often referred to as the 'blueberry muffin model'?
How did Thomson deduce that atoms must also contain a positive charge?
How did Thomson deduce that atoms must also contain a positive charge?
What did Robert Millikan use to determine the charge of an electron?
What did Robert Millikan use to determine the charge of an electron?
What was the significance of the charge-to-mass ratio found by Thomson in Millikan's experiments?
What was the significance of the charge-to-mass ratio found by Thomson in Millikan's experiments?
What did Millikan adjust to halt the fall of charged oil droplets?
What did Millikan adjust to halt the fall of charged oil droplets?
What hypothesis did Thomson make about the structure of an atom?
What hypothesis did Thomson make about the structure of an atom?
What was the calculated mass of an electron according to Millikan?
What was the calculated mass of an electron according to Millikan?
Study Notes
Early Atomic Theory
- Antoine Lavoisier and others conducted accurate quantitative measurements of chemical reactions in the late 1700s
- John Dalton proposed the first modern atomic theory in the early 1800s, stating that elements consist of atoms, which cannot be created, destroyed, or divided, and that atoms of the same element have identical properties
The Discovery of the Electron
- J.J. Thomson conducted cathode ray tube experiments in the late 1800s, which provided evidence for the existence of the electron, a negatively charged subatomic particle
- Thomson determined the charge-to-mass ratio of an electron
- Thomson’s “blueberry muffin model” posited that atoms consist of a diffuse cloud of positive charge with negatively charged electrons embedded randomly
Robert Millikan’s Oil Drop Experiment
- Robert Millikan determined the charge of an electron using charged oil drops in the early 1900s
- Millikan used the charge of the electron and the charge-to-mass ratio determined by Thomson to calculate the mass of the electron
Rutherford’s Gold Foil Experiment
- Ernest Rutherford conducted the gold foil experiment in the early 1900s
- Rutherford bombarded thin gold foil with alpha particles
- Rutherford observed that most of the alpha particles passed straight through the foil, while some were deflected at various angles, and others were reflected back toward the source
- Rutherford concluded that the atom's positive charge is concentrated in a small, dense nucleus with negatively charged electrons orbiting around it
- Rutherford's model suggested that the atom is mostly empty space.
The Quantum Mechanical Model
- The quantum mechanical model describes the electron as a standing wave that can occupy a series of orbitals.
- Each orbital has a prescribed possible energy and spatial distribution.
- Heisenberg's uncertainty principle states that it is impossible to know both the position and the speed of a particle simultaneously.
- The ground state of a hydrogen atom is when its single electron resides in a low-energy orbital.
- Electrons can move between orbitals by absorbing or emitting quanta of energy.
- The location of electrons is given by a probability distribution.
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Description
Explore the foundational concepts of atomic theory and the discovery of the electron through pivotal experiments by Lavoisier, Dalton, Thomson, and Millikan. This quiz covers key historical developments and experiments that shaped our understanding of atomic structure. Test your knowledge on the early theories and discoveries that defined modern chemistry.
