AP Chapter 7-8: Quantum Chemistry & Periodic Relationships Name Warm-Ups (Show your work for credit)

Transcription

1 AP Chapter 7-8: Quantum Chemistry & Periodic Relationships Name Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

2 AP Chemistry: Quantum Chemistry & Periodic Relationships 2 Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

3 AP Chemistry: Quantum Chemistry & Periodic Relationships 3 Warm-ups and problems will be collected before you take the test. Read Chapter 7: Quantum Theory and the Electronic Structure of Atoms Read Chapter 8: Periodic Relationships among the Elements Answer the following problems in the space provided. For problems involving an equation, carry out the following steps: 1. Write the equation. 2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work. Electromagnetic Radiation 1. What is the range of wavelengths (in nanometers) and range of frequencies (in Hertz) of visible light? 2. What is the frequency of light having a wavelength of 456 nm? 3. What is the wavelength in nanometers of radiation having a frequency of 2.45 X 10 9 Hz? (This is the type of radiation used in microwave ovens.) 4. How many minutes would it take a radio wave to travel from the planet Venus to Earth? (Average distance from Venus to Earth = 28 million miles and 1 mile = 1609 m.) 5. What is the wavelength, in nm, of radiation that has an energy content of 1.0 x 10 3 kj/mol? In which region of the electromagnetic spectrum is this radiation found? 6. Only a fraction of the electrical energy supplied to a tungsten light bulb is converted to visible light. The rest of the energy shows up as infrared radiation (felt as heat). A 75-W light bulb converts 15.0 percent of the energy supplied to it into visible light (assume the wavelength to be 550 nm). How many photons are emitted by the light bulb per second? (1 W = 1 J/s.) 7. What is the energy of a mole of photons with a wavelength of 600 nm?

4 AP Chemistry: Quantum Chemistry & Periodic Relationships 4 8. The photodissociation of water: H 2O(l) + h H 2(g) + ½ O 2(g) has been suggested as a source of hydrogen. The H o rxn for the reaction, calculated from thermochemical data, is kj per mole of water decomposed. Calculate the maximum wavelength in nm that would provide the necessary energy. What is the color of this light? Bohr Theory of the Hydrogen Atom 9. Both a hydrogen atom and a helium cation (He + ) have only one electron. Assuming the electron in each is the same distance from the nucleus, use Coluomb s law to determine which electron is attracted to the nucleus with greater force. Calculate the ratio of this force for the two species. 10. State Bohr s explanation of the emission line spectrum of hydrogen. 11. The energy of an electron in a hydrogen atom is given by the equation: E n = -2.18E-18J (1/n 2 ), where n represents the energy level of the electron. Explain the meaning of the negative sign. Quantum Mechanics 12. Define orbital. 13. An orbital is defined by three quantum numbers. List each and state what each tells about the orbital. 14. An electron in an atom is in the n = 3 energy level. (a) How many orbitals are associated with this energy level? (b) List all the orbitals on this energy level. (c) What is the maximum number of electrons on this energy level? 15. Calculate the total number of electrons that can be held in energy level 1, energy level 2, and energy level 3. What simple formula, in terms of principal quantum number n, gives this result?

5 AP Chemistry: Quantum Chemistry & Periodic Relationships Explain, in terms if shielding, why the 3s, 3p, and 3d orbitals have the same energy in a hydrogen atom but different energies in a many-electron atom? 17. Explain Hund s rule using nitrogen as an example. 18. Which of the following species has the most unpaired electrons? S +, S, or S -. Explain. 19. Write the box diagram and electron configuration of: (a) phosphorous (b) vanadium 20. Using only the Periodic Table as a guide, write the shorthand electron configuration of the following elements, and state whether each is paramagnetic or diamagnetic: (a) cadmium (b) iron 21. Explain why the ground-state electron configurations of Cr and Cu are different from what we might expect. 22. Consider the energy levels of a hypothetical atom: E 4-1.0E-19 J E 3-5.0E-19 J E 2-1.0E-18 J E 1-1.5E-18 J (a) What wavelength photon is needed to excite an electron from E 1 to E 4? (b) When an electron drops from E 3 to E 1, the atom is said to undergo emission. Calculate the energy and wavelength of the emitted photon.

6 AP Chemistry: Quantum Chemistry & Periodic Relationships How many valence electrons are in each of the following atoms? (a) N (b) Fe (c) C (d) Cu 24. Identify the following elements: (a) [Xe]6s 2 (b) 1s 2 2s 2 2p 3 (c)1s 2 2s 2 2p 4 3s 1 (d) [Ne]3s 2 3p Explain how photoelectron spectroscopy (PES) is used to verify the quantum model. Why are high energy photon such as UV and X-rays used as the source in PES? 26. How many peaks would the PES of lithium show? Explain. 27. The photoelectron spectrum for potassium is shown below. Ionization Energy (Megajoules per mole) a. Label the subshell represented by each peak in the diagram above. b. What is the wavelength of the photon that gives rise to the lowest energy peak in the PES? Periodic Classification of Elements 28. What is the meaning of the word periodic in the name Periodic Table? 29. The boiling points of neon and krypton are C and C, respectively. Using these data, estimate the boiling point of argon.

7 AP Chemistry: Quantum Chemistry & Periodic Relationships A neutral atom of a certain element has 17 electrons. Without consulting a periodic table (a) write the ground-state electron configuration of the element. (b) classify the element (representative, transition, inner transition). (c) determine whether the atoms of this element are diamagnetic or paramagnetic. 31. Why do most transition elements have two valence electrons? 32. A M 2+ ion derived from a metal in the first transition metal series has four electrons in the 3d subshell. What element might M be? 33. A metal ion with a net +3 charge has five electrons in the 3d subshell. Identify the element. Periodic Variation in Physical Properties 34. Explain, in terms of Coulomb s law and shielding, why the valence electron in fluorine feels a stronger force of attraction to the nucleus than does the valence electron in oxygen. 35. Explain, in terms of energy levels, shielding, and/or effective nuclear charge, which atoms is larger. (a) Ar vs. Ne (b) K vs Ar (c) S vs. P 36. Explain why, for isoelectronic ions, the anions are larger than the cations. Give a specific example in your explanation. 37. Rank from smallest to largest the radii of the following species: Cu, Cu 2+, Cu +. Explain.

8 AP Chemistry: Quantum Chemistry & Periodic Relationships Define first ionization energy and second ionization energy. 39. Explain, in terms of energy levels, shielding, and/or effective nuclear charge, the general trend of ionization energy: (a) left to right across a period (b) top to bottom down a group 40. In general, ionization energy increases from left to right across a given period. Explain these exceptions: (a) aluminum has a lower first ionization energy than magnesium. (b) sulfur has a lower first ionization energy than phosphorous 41. The PES spectra of potassium and calcium are shown in the table below. PES Spectra of K and Ca, in MJ/mol Element 1s 2s 2p 3s 3p 4s K Ca (a) Explain why the energies of the sublevels of Ca are larger than those of K. (b) Referring to the PES values, explain why a Ca atom is smaller than a K atom. (c) Referring to the PES values, which atom has a larger first ionization energy? Explain. 42. Define electronegativity.

9 AP Chemistry: Quantum Chemistry & Periodic Relationships Rank the following elements in order of increasing electronegativity: As, F, Br, Sr, and O. Variation in Chemical Properties 44. Why are Group 11 elements more stable than Group 1 elements even though they have the same number of valence electrons? 45. Which oxide is more basic, MgO or BaO? Why? 46. Define and give an example of an amphoteric oxide. 47. Write the formulas and names of the oxides of the second-period elements (Li to N). Identify the oxides as acidic, basic, or amphoteric. 48. Based on knowledge of the electronic configuration of titanium, state which of the following compound(s) of titanium are unlikely to exist: K 3TiF 6, K 2Ti 2O 5, TiCl 3, K 2TiO 4, K 2TiF Why is the first member of most groups somewhat different than the other members of that group? 50. What is meant by diagonal relationships, and what is the cause? Give an example. 51. Does hydrogen belong in Group 1or 17? Give an example of the reaction of a metal hydride with water. 52. Give an example of each reaction. (a) Metal oxide + water? (b) Nonmetal oxide + water?