Chapter 9 - Atomic Physics - Palomar：9章原子物理-帕洛马.doc

Chapter 9 - Atomic PhysicsANSWERS TO SHORT-ANSWER QUESTIONS 3. Thomsons “plum pudding” model pictured the atom as consisting of electrons randomly positioned like raisins in an otherwise homogeneous mass of positively charged “pudding.” Thomsons model was abandoned when Rutherford discovered that each atom had a tiny core, or nucleus, in which 99.9% of the mass and all the positive charge were concentrated and around which the electrons circulated. 6. Something is quantized when it is restricted to certain discrete values rather than having a continuous range of values. 7. A proton is a positively charged subatomic particle found in the nuclei of atoms. A photon is a quantum, or “particle,” of electromagnetic radiation. 8. Frequency and wavelength are inversely proportional. 9. A photon of red light has less energy, lower frequency, and longer wavelength than a photon of violet light.11. Albert Einstein. The theory of relativity.15. The ground state for an electron is the lowest energy state. Energy states above the ground state are called excited states.17. The four discrete lines in the emission spectrum of hydrogen correspond to electron transitions down to n = 2 from n = 6, 5, 4, and 3.18. The four discrete lines in the absorption spectrum of hydrogen correspond to electron transitions up to n = 6, 5, 4, and 3 from n = 2.19. In fluorescence, the light stops coming from the sample at the instant the exciting source is removed. In phosphorescence, the light continues to be emitted from the sample for a period of time. 20. The potato contains water, whereas the ceramic plate does not.25. It is impossible to know a particles exact position and velocity simultaneously.26. Only particles of atomic and subatomic size would have their velocities significantly changed by being hit by photons when locating their positions. 30. Schrdinger.31. Quantum model, or electron cloud model.ANSWERS TO APPLYING-YOUR-KNOWLEDGE QUESTIONS 4. A quantized cruise control might be digital and allow speeds to be set on 5 mph units, such as 50 or 55 mph, but not 51 mph. 5. “Black light” is the popular term for the longer-wavelength portion of the ultraviolet region. You would explain that the photons of ultraviolet light were causing electrons in the atoms of the paint to be excited to upper energy levels. Some of the electrons return to their ground states in steps, emitting some photons lower in energy than the UV photons that excited them. Some of the lower-energy photons emitted are in the visible region, making the picture glow. We call the phenomenon fluorescence. 7. Mercury vapor or sodium vapor lights give off only certain wavelengths of light (those in their line emission spectra). Thus only certain colors are available to be absorbed or reflected from the variously colored cars. The reflected light by which we see the cars thus has a different overall composition (color) from reflected sunlight or reflected light from an incandescent bulb. 8. A car is much too large to allow v (or x) to be of significant size.Chapter 11 The Chemical ElementsANSWERS TO SHORT-ANSWER QUESTIONS 3. Illustrations b and d show different atoms and/or molecules and thus represent mixtures. Illustration e shows identical molecules composed of the same two elements and so represents a compound. Illustrations a and c show identical atoms and identical diatomic molecules of atoms of the same element, respectively, and thus represent elements. Illustration c shows diatomic molecules of an element, whereas e shows diatomic molecules of a compound. 4. A pure substance is a type of matter in which all samples have fixed composition and identical properties, whereas a mixture is a type of matter composed of varying proportions of two or more substances that are just physically mixed, not chemically combined. Thus samples of a mixture can have variable composition and properties. 5. Mixtures can be separated into, and prepared from, pure substances by physical processes. 6. An element is a pure substance in which all the atoms have the same number of protons; elements cannot be further broken down by chemical processes. A compound is a substance composed of two or more elements chemically combined in a definite, fixed proportion by mass.12. At present, about 115 elements are known, 88 of which occur naturally on Earth. 13. (a) Oxygen and silicon. (b) Iron and nickel. (c) Oxygen and carbon. (d) Nitrogen and oxygen. (e) Hydrogen and helium.14. O315. Dmitri Mendeleev developed the periodic table in 1869.16. Atomic number is now used. The periodic trends in the table are based on atomic number, which correlates more exactly with electron configuration than does atomic mass.17. The properties of elements are periodic functions of their atomic numbers.18. (a) Periods. (b) Groups.19. The valence electrons are the ones that form chemical bonds.23. Mercury and bromine are liquid. Hydrogen, oxygen, nitrogen, fluorine, and chlorine, (plus six noble gases) are gases.24. Atomic size (a) decreases from left to right across a period, and (b) increases down a group.26. (a) An atom is the smallest particle of an element; a molecule is an electrically neutral particle composed of two or more atoms chemically bound together.(b) An atom is electrically neutral; an ion has an electrical charge.(c) A molecule is an electrically neutral particle composed of two or more atoms; a polyatomic ion is an electrically charged particle composed of two or more atoms.28. Because they have the same number of valence electrons.29. The noble gases are chemically unreactive. They have low boiling and melting points.30. Fluorine and chlorine are gases, bromine is liquid, and iodine is solid. Fluorine is the most reactive element.31. Sodium iodide is added to prevent thyroid problems due to iodine deficiency.32. NaHCO3 is baking soda.34. The Hindenburg syndrome is the term applied to the reluctance to use hydrogen as a fuel.ANSWERS TO APPLYING-YOUR-KNOWLEDGE QUESTIONS 3. Graphite makes a good lubricant because of its slipperiness, so the key should turn easily. 4. Being “snobs” refers to the noble gases lack of chemical reactivity, or “interaction,” with other elements.Chapter 12 Chemical BondidngANSWERS TO SHORT-ANSWER QUESTIONS 1. The law of conservation of mass states that no detectable change in total mass occurs during a chemical reaction. For example, if a sealed vessel containing copper and oxygen has a mass of 245.00 g and is heated so that copper oxide is formed, the vessel and its contents will still have a mass of 245.00 g after reaction. 8. The percentage abundance of isotopes of a given element is the same in all natural samples on Earth. This means that each element has an unvarying average mass (the atomic mass) that can be assigned to its atoms. The law of definite proportions holds whether atoms of a given element all have the same mass or an unvarying average mass. 9. In forming compounds, atoms tend to gain, lose, or share valence electrons to achieve the electron configurations of the noble gases. That is, they tend to get eight electrons (an octet) in the outer shell (except for H, which tends to get two electrons in the outer shell, like the configuration of He). Hydrogen is an exception because it must use the first shell, which can hold only two electrons.10. The valence electrons, those in the outermost shell of the atom.11. Atoms with three or fewer electrons tend to lose them; atoms with four or more valence electrons tend to gain more electrons.12. By transfer of electrons.19. If it conducts electricity when molten, it is ionic.20. An aqueous solution of salt contains an abundance of mobile ions and thus can conduct electricity. An aqueous solution of table sugar has only mobile molecules (neutral entities) and thus cannot conduct electricity.22. Covalent compounds are formed by the sharing of pairs of electrons. 26. A polar covalent bond.28. Geometry, or shape.29. (a) Ionic compounds are always solid; covalent compounds may be solid, liquid, or gas.(b) Ionic compounds conduct electricity when melted; covalent compounds do not conduct.32. Like dissolves like, which means that polar liquids tend to dissolve polar and ionic compounds but not covalent compounds, whereas covalent liquids tend to dissolve other covalent compounds but not polar and ionic substances.33. A hydrogen bond is a dipole-dipole force between a hydrogen atom a