Frosh PhySci - Atomic Theory Flashcards
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True or false: Thomson won a Nobel Prize for his discovery of protons.
false
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J. J. Thomson discovered the subatomic particles called _____.
electrons
What is a cathode ray tube?
A cathode ray tube is a glass tube from which virtually all of the air has been removed. It contains a piece of metal called an electrode at each end. One electrode is negatively charged, and the other electrode is positively charged. When high-voltage electric current is applied to the end plates, a cathode ray travels from the negative to positive electrode.
Describe Thomson’s cathode ray tube experiments.
Thomson’s did experiments to find out whether a cathode ray is a ray of energy, like a ray of light, or a stream of moving particles. He tested these ideas by placing negative and positive plates along the sides of the cathode ray tube to see how the cathode ray would be affected.
What evidence led Thomson to conclude that cathode rays consist of streams of tiny particles of matter rather than rays of energy?
The cathode rays appeared to be repelled by the negative plate and attracted by the positive plate. This meant that the rays were negative in charge and had mass. These are properties of matter, not energy, so he concluded that the cathode rays must consist of streams of tiny particles rather than rays of energy.
Thomson knew that the particles he discovered were smaller than atoms because of their
a) charge.
b) color.
c) mass.
d) volume.
c) mass
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Thomson’s model of the atom is called the _____ model.
plum pudding
Why did Thomson think that atoms must contain positive charges?
Thomson thought that atoms must contain positive charges because atoms contain negative electrons yet are neutral in charge. They would have to have positive charges to cancel out the negative charges of the electrons.
Thomson thought that the positive charges in an atom were
a) concentrated in the nucleus.
b) clumped into small clusters like plums.
c) spread throughout the atom.
d) none of the above
c) spread throughout the atom.
True or false: Thomson’s research proved Dalton’s earlier claim about the smallest particles of matter.
False
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Rutherford first discovered the _____ of the atom.
nucleus
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Rutherford later discovered the subatomic particles called _____.
Protons
Rutherford’s research used positive alpha particles, which we now know are helium _____.
nuclei
Describe the setup of Rutherford’s gold foil experiments.
Rutherford aimed a beam of alpha particles at a sheet of very thin gold foil. Surrounding the sheet of gold foil, he placed a screen that would glow when alpha particles struck it. Its purpose was to detect where the alpha particles went after interacting with the gold foil. A small slit in the screen allowed a beam of alpha particles to reach the gold foil from a particle emitter.
In Rutherford’s’ experiments, most of the alpha particles
a) were deflected by the gold foil.
b) passed straight through the gold foil.
c) bounced straight back from the gold foil.
d) none of the above
b) passed straight through the gold foil.
From his results, Rutherford concluded that the positive charge of an atom is
a) less than the negative charge of the atom.
b) spread evenly throughout the atom.
c) concentrated in a tiny area at the center of the atom.
d) two of the above
c) concentrated in a tiny area at the center of the atom.
True or false: Based on his research, Rutherford thought that most of an atom consists of empty space.
True
True or false: Rutherford predicted the existence of neutrons but failed to find them.
True
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Rutherford’s model of the atom is called the _____ model.
planetary
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Compare and contrast Rutherford’s and Thomson’s models of the atom.
Both Rutherford’s and Thomson’s models of the atom include negative electrons and areas of positive charge. Thomson thought the atom was mostly a mass of positive charge with electrons scattered throughout it, like plums in a pudding. Rutherford thought that the positive charge was concentrated in a tiny nucleus at the center of the atom, with electrons moving around it like planets around the sun.
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What are protons?
Protons are positively charged particles inside the nuclei of atoms.
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True or false: Protons are one of three main types of particles that make up atoms.
True
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True or false: Protons are found only in the atomic nucleus.
True
Which of the following correctly describes a proton?
a) It has an electrical charge of +2.
b) It has a mass of 1 mg.
c) It has a diameter of 1.7 x 10-27 km.
d) none of the above
d) none of the above
