Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (c) The cathode ray is deflected away from a positively charged plate.
Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 91
What discovery about atomic structure was made from the results of Rutherford's gold foil experiment?

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Understand the setup of Rutherford's gold foil experiment: A beam of alpha particles was directed at a thin sheet of gold foil.
Recognize the expected outcome based on the plum pudding model: Most particles should pass through with only slight deflections, as the atom was thought to be a diffuse cloud of positive charge.
Observe the actual results: While most alpha particles passed through the foil, some were deflected at large angles, and a few even bounced back.
Analyze the implications: The significant deflections suggested that the positive charge in an atom is concentrated in a small, dense region (later called the nucleus), rather than being spread out.
Conclude the discovery: Rutherford's experiment led to the realization that an atom consists of a small, dense nucleus surrounded by electrons, overturning the plum pudding model and leading to the development of the nuclear model of the atom.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Atomic Structure
Atomic structure refers to the arrangement of protons, neutrons, and electrons within an atom. The nucleus, containing protons and neutrons, is surrounded by electrons in various energy levels. Understanding atomic structure is fundamental to grasping how atoms interact and bond with one another.
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Atom Structure
Rutherford's Gold Foil Experiment
Rutherford's gold foil experiment, conducted in 1909, involved firing alpha particles at a thin sheet of gold. The unexpected deflection of some particles led to the conclusion that atoms have a small, dense nucleus, which contains most of the atom's mass and positive charge, while the rest of the atom is mostly empty space.
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Rutherford Gold Foil Experiment
Nuclear Model of the Atom
The nuclear model of the atom, proposed by Rutherford, describes the atom as having a central nucleus surrounded by orbiting electrons. This model replaced the earlier plum pudding model and established the concept of a concentrated positive charge in the nucleus, fundamentally changing the understanding of atomic structure and leading to further developments in atomic theory.
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Bohr Model of the Atom
Related Practice
Textbook Question
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Textbook Question
Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (f) By measuring the deflection of the cathode ray beam caused by electric fields of known strength, the charge-to-mass ratio of the electron was calculated.
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Textbook Question
Which of the following charges is not possible for the over-all charge on an oil droplet in Millikan's experiment? For this problem, we'll round the currently accepted charge of an electron to 1.602 * 10-19 C.(a) -1.010 * 10-18 C (b) -8.010 * 10-19 C(c) -2.403 * 10-18 C
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Textbook Question
Prior to Rutherford's gold foil experi-ment, the 'plum pudding' model of the atom represented atomic structure. In this model, the atom is composed of elec-trons interspersed within a positive cloud of charge. If this were the correct model of the atom, predict how the results of Rutherford's experiment would have been different. (a) The alpha particles would pass right through the gold foil with little to no deflection.(b) Most of the alpha particles would be deflected back toward the source.(c) Most of the alpha particles would be absorbed by the atom and neither pass through nor be deflected from the gold foil.
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Textbook Question
A period at the end of sentence written with a graphite pencil has a diameter of 1 mm. If the period represented the nucleus, approximately how large is the diameter of the entire atom in units of m?
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Textbook Question
A period at the end of sentence written with a graphite pen-cil has a diameter of 1 mm. How many carbon atoms would it take to line up across the period if a single carbon atom has a diameter of 150 pm?
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