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Ch.2 - Atoms, Molecules, and Ions
Chapter 2, Problem 18b

Millikan determined the charge on the electron by studying the static charges on oil drops falling in an electric field (Figure 2.5). A student carried out this experiment using several oil drops for her measurements and calculated the charges on the drops. She obtained the following data: Droplet Calculated Charge (C) A 1.60 * 10-19 B 3.15 * 10-19 C 4.81 * 10-19 D 6.31 * 10-19 (b) What conclusion can the student draw from these data regarding the charge of the electron?

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Millikan's Oil Drop Experiment

Millikan's Oil Drop Experiment was a groundbreaking study that measured the charge of the electron by observing tiny oil droplets suspended in an electric field. By adjusting the electric field strength, Millikan could balance the gravitational force on the droplets, allowing him to calculate the charge on each droplet. This experiment provided crucial evidence for the quantization of electric charge, showing that charges are multiples of a fundamental unit.
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Quantization of Charge

The quantization of charge refers to the principle that electric charge exists in discrete units rather than a continuous range. In the context of Millikan's experiment, the calculated charges of the oil droplets were found to be integer multiples of a fundamental charge value, which is the charge of a single electron (approximately 1.60 x 10^-19 coulombs). This concept is essential for understanding the nature of electric charge and its implications in atomic theory.
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Data Analysis and Conclusion Drawing

Analyzing experimental data involves examining the results to identify patterns or relationships. In this case, the student must look for a common factor among the calculated charges of the oil droplets. By recognizing that all measured charges are multiples of the smallest charge (1.60 x 10^-19 C), the student can conclude that the charge of the electron is indeed 1.60 x 10^-19 C, reinforcing the concept of quantized charge.
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Related Practice
Textbook Question

An unknown particle is caused to move between two electrically charged plates, as illustrated in Figure 2.7. You hypothesize that the particle is a proton. (a) If your hypothesis is correct, would the particle be deflected in the same or opposite direction as the b rays?

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Textbook Question

An unknown particle is caused to move between two electrically charged plates, as illustrated in Figure 2.7. You hypothesize that the particle is a proton. (b) Would it be deflected by a smaller or larger amount than the b rays?

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What fraction of the a particles in Rutherford's gold foil experiment are scattered at large angles? Assume the gold foil is two layers thick, as shown in Figure 2.9, and that the approximate diameters of a gold atom and its nucleus are 270 pm and 1.0 * 10–2 pm, respectively. Hint: Calculate the cross sectional area occupied by the nucleus as a fraction of that occupied by the atom. Assume that the gold nuclei in each layer are offset from each other.
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Textbook Question

Millikan determined the charge on the electron by studying the static charges on oil drops falling in an electric field (Figure 2.5). A student carried out this experiment using several oil drops for her measurements and calculated the charges on the drops. She obtained the following data: Droplet Calculated Charge (C) A 1.60 * 10-19 B 3.15 * 10-19 C 4.81 * 10-19 D 6.31 * 10-19 (c) What value (and to how many significant figures) should she report for the electronic charge?

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Textbook Question

The radius of an atom of tungsten (W) is about 2.10 A . (c) If the atom is assumed to be a sphere, what is the volume in m3 of a single W atom?

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Textbook Question

The radius of an atom of copper (Cu) is about 140 pm. (c) If you assume that the Cu atom is a sphere, what is the volume in cm3 of a single atom?

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