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Questions and Answers
One of the following is not a main subatomic particle. Which is it?
One of the following is not a main subatomic particle. Which is it?
- Electron
- Proton
- Positron (correct)
- Neutron
Dalton assumed that atoms could not be broken down further.
Dalton assumed that atoms could not be broken down further.
True (A)
Investigations in the late ___ proved that atoms can indeed be broken down into smaller particles.
Investigations in the late ___ proved that atoms can indeed be broken down into smaller particles.
1800s
J.J. Thomson carried out experiments with which equipment?
J.J. Thomson carried out experiments with which equipment?
Cathode rays were shown to be streams of _____ particles.
Cathode rays were shown to be streams of _____ particles.
Millikan's oil drop experiment determined the mass of which particle?
Millikan's oil drop experiment determined the mass of which particle?
Complete atoms are electrically:
Complete atoms are electrically:
Who discovered the proton in 1886?
Who discovered the proton in 1886?
The cathode ray was composed of particles.
The cathode ray was composed of particles.
The cathode rays were deflected towards a negatively charged metal plate.
The cathode rays were deflected towards a negatively charged metal plate.
The value for the charge on the electron depends on the gas used in the cathode ray tube.
The value for the charge on the electron depends on the gas used in the cathode ray tube.
The neutron has approximately the same mass as the proton.
The neutron has approximately the same mass as the proton.
The proton was first called a canal ray.
The proton was first called a canal ray.
The electron weighs about ___ the mass of the hydrogen atom.
The electron weighs about ___ the mass of the hydrogen atom.
The ___ is the positively charged electrode in the cathode ray tube.
The ___ is the positively charged electrode in the cathode ray tube.
The cathode ray deflection in a __ field showed it was a ____ charged particle.
The cathode ray deflection in a __ field showed it was a ____ charged particle.
JJ Thomson developed the _______ model of the atom.
JJ Thomson developed the _______ model of the atom.
Rutherford performed the ____ foil experiment to study atomic structure.
Rutherford performed the ____ foil experiment to study atomic structure.
Rutherford's experiment used ____ to bombard the foil.
Rutherford's experiment used ____ to bombard the foil.
The nucleus of the atom is composed of:
The nucleus of the atom is composed of:
Rutherford felt that all the atom's positive charge was in the nucleus.
Rutherford felt that all the atom's positive charge was in the nucleus.
Rutherford's experiments showed the location of the electron.
Rutherford's experiments showed the location of the electron.
In Rutherford's experiment, most of the particles passed through the gold foil.
In Rutherford's experiment, most of the particles passed through the gold foil.
None of the particles in Rutherford's experiment bounced back toward the source.
None of the particles in Rutherford's experiment bounced back toward the source.
Rutherford's experiment showed that most of the atom was ____.
Rutherford's experiment showed that most of the atom was ____.
The particles used in Rutherford's experiment were about __ times the size of the hydrogen atom and were _____ charged.
The particles used in Rutherford's experiment were about __ times the size of the hydrogen atom and were _____ charged.
Rutherford's atomic model became known as the nuclear model.
Rutherford's atomic model became known as the nuclear model.
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Study Notes
Subatomic Particles
- Main subatomic particles include protons, electrons, and neutrons; positrons are not considered a main subatomic particle.
- Dalton's atomic theory initially stated that atoms could not be divided further.
- Investigations in the late 1800s revealed that atoms could be broken down into smaller parts.
Cathode Rays
- J.J. Thomson used a cathode ray tube to conduct experiments on atomic structure.
- Cathode rays consist of negatively charged particles.
- The charge of the electron does not vary with the gas used in cathode ray tubes.
Key Experiments
- Millikan's oil drop experiment measured the mass of the electron.
- Rutherford's gold foil experiment aimed to uncover atomic structure, revealing that most of the atom is empty space.
- Alpha particles were used to bombard the foil in Rutherford's experiment.
Atomic Composition
- Atoms are electrically neutral overall despite containing charged particles.
- The nucleus contains protons and neutrons but no electrons.
- The neutron has a similar mass to the proton, contributing to atomic mass.
Charge and Mass of Particles
- Protons carry a relative charge of +1 and a relative mass of 1.
- Neutrons have a neutral charge (0) and a relative mass of 1.
- Electrons have a relative charge of -1 and a relative mass of 1/1840 compared to a proton.
Historical Discoveries
- Eugene Goldstein discovered the proton in 1886, originally referred to as canal rays.
- Thomson's atomic model is often referred to as the "plum pudding" model.
Rutherford’s Insights
- Rutherford concluded that all of an atom's positive charge is concentrated in the nucleus.
- Most particles in his experiment passed through the gold foil, indicating that the atom is largely empty.
- Some particles bounced back, indicating a dense, compact nucleus within the atom.
Visual Representation
- The atomic structure can be summarized as protons and neutrons in the nucleus, surrounded by an electron cloud, illustrating the arrangement and relative sizes of subatomic particles.
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