1.
Suppose you wanted to estimate the age of an archaeological site using radiometric dating. Would you use the uranium-lead system described in section 2.1, or would you evaluate a radioisotope that had a shorter half-life? Explain your answer.
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2.
Hydrogen bonds form because the partial electric charges on polar molecules attract. Covalent bonds form because of the electrical attractions between electrons and protons. Covalent bonds are much stronger than hydrogen bonds. Explain why, in terms of the electrical attractions involved.
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3.
Oxygen is extremely electronegative, meaning that its nucleus pulls in electrons shared in covalent bonds. Because these electrons are close to the oxygen nucleus, they have lower potential energy. Explain the changes in electron position that are illustrated in Figure 2.12 in terms of oxygen’s electronegativity.
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4.
When nuclear reactions take place, some of the mass in the atoms involved is converted to energy. The energy in sunlight is created during nuclear fusion reactions on the Sun. Explain what astronomers mean when they say that the Sun is burning down and that it will eventually burn out.
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