The first 25 years of the twentieth century were momentous for the rapid pace of change in scientists’ understanding of the nature of matter. (a) How did Rutherford’s experiments on the scattering of alpha particles by a gold foil set the stage for Bohr’s theory of the hydrogen atom?

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Rutherford's gold foil experiment involved directing a beam of alpha particles at a thin sheet of gold foil and observing their scattering patterns.

Most alpha particles passed through the foil with little or no deflection, but a small fraction were deflected at large angles, and some even bounced back.

Rutherford concluded that the atom is mostly empty space with a small, dense, positively charged nucleus at its center, which caused the deflection of alpha particles.

This nuclear model of the atom challenged the previous plum pudding model and set the stage for further exploration of atomic structure.

Bohr built upon Rutherford's model by proposing that electrons orbit the nucleus in specific energy levels, explaining the stability of atoms and the emission spectra of hydrogen.

Key Concepts

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

Rutherford's Gold Foil Experiment

Rutherford's gold foil experiment demonstrated that atoms consist of a small, dense nucleus surrounded by mostly empty space. When alpha particles were directed at a thin gold foil, most passed through, but some were deflected at large angles. This unexpected result led to the conclusion that the nucleus contains most of the atom's mass and positive charge, fundamentally changing the model of atomic structure.

Atomic Model Evolution

The evolution of atomic models reflects the progression of scientific understanding. Prior to Rutherford, the plum pudding model suggested that electrons were distributed within a positively charged 'soup.' Rutherford's findings prompted a shift to a nuclear model, which set the groundwork for Bohr's theory, where electrons occupy specific energy levels around the nucleus, explaining atomic stability and spectral lines.

Bohr's Theory of the Hydrogen Atom

Bohr's theory introduced quantized energy levels for electrons in hydrogen, proposing that electrons orbit the nucleus at fixed distances. This model explained the discrete spectral lines observed in hydrogen's emission spectrum, as electrons transition between these energy levels. Bohr's approach built on Rutherford's nucleus concept, providing a clearer understanding of atomic structure and behavior.

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Bohr Model of the Atom

Related Practice

Textbook Question

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (d) Using their electron configurations, account for the fact that Zr and Hf form chlorides MCl₄ and oxides MO₂.

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Textbook Question

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr’s laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (c) Solid zirconium dioxide, ZrO₂, reacts with chlorine gas in the presence of carbon. Starting with a 55.4-g sample of ZrO₂, calculate the mass of ZrCl₄ formed, assuming that ZrO₂ is the limiting reagent and assuming 100% yield.

Textbook Question

The first 25 years of the twentieth century were momentous for the rapid pace of change in scientists' understanding of the nature of matter. (b) In what ways is de Broglie's hypothesis, as it applies to electrons, consistent with J. J. Thomson's conclusion that the electron has mass? In what sense is it consistent with proposals preceding Thomson's work that the cathode rays are a wave phenomenon?

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Textbook Question

The two most common isotopes of uranium are 235U and 238U. (b) Using the periodic table in the frontinside cover, write the electron configuration for a U atom.

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Textbook Question

The two most common isotopes of uranium are 235U and 238U. (d) 238U undergoes radioactive decay to 234Th. How many protons, electrons, and neutrons are gained or lost by the 238U atom during this process? (e) Examine the electron configuration for Th in Figure 6.31. Are you surprised by what you find? Explain.

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