Homework Packet Unit 2. b. Al 3+, F, Na +, Mg 2+, O 2

Transcription

1 Name Period Homework Packet Unit 2 1. Which of the following is the correct empirical formula for a compound that has 37.5% C, 12.6% H, and 49.9% O? (A) C 2 H 4 O (B) CH 4 O 2 (C) CH 5 O 2 (D) CH 4 O (E) C 2 H 8 O 2 2. How many moles of carbon dioxide gas take up a volume of 5.33 L at STP? (A) mole (B) 119 mol (C) mol (D) mol (E) mol 3. Which of the following is least metallic? (A) I (B) O (C) Cs (D) K (E) Te 4. What element in row 3 is classified as a metalloid? 8. For which of the following elements would the valence electron or electrons be most shielded from the charge in the nucleus? (A) Ba (B) Ca (C) Xe (D) Rb (E) F 9. Which of the following ions is largest in size? (A) O 2 (B) Al 3+ (C) Na + (D) F (E) Mg Arrange the following atoms or ions in order of increasing size: a. Br, Ca 2+, K +, Se 2 b. Al 3+, F, Na +, Mg 2+, O 2 c. As 3, Ca 2+, Cl, K + 5. The element with the atomic number 118, if discovered, will be in what family? 11. Atomic radius generally increases as we go down a group in the periodic table. a. Explain why. 6. What family of elements consists of soft metals of low melting point, all of which react vigorously with water at room temperature? 7. In Group IA, for which element would the valence electron be most shielded from the charge in the nucleus? b. Explain the inconsistency of the atomic radius of hafnium: Atomic radii in pm Sc: 157; Ti: 148 Y: 169; Zr: 159 La: 192; Hf: 148

2 12. In the upper right hand corner of the periodic table are found elements which (A) have low ionization energies. (B) form acidic oxides. (C) form simple ions with positive oxidation states. (D) tend to form ionic bonds with other elements near them. (E) have high boiling points. 13. What is the meaning of a positive electron affinity? Is energy released or absorbed? Compared to most other atoms, does the atom have a higher or lower tendency to add another electron? 14. Which of the following atoms would have the greatest (most negative) electron affinity? (A) Ge (B) As (C) Se (D) Sn (E) Sb 15. For the following problem, increased electron affinity means more negative electron affinity. Given the following: I. Ionization energy II. Electron affinity III. Atomic radius In general, as one moves across a row of the periodic table from the alkali metals to the halogens: (A) I, II and III will decrease. (B) I, II and III will increase. (C) I will increase, II and III will decrease. (D) I and II will increase, III will decrease. (E) I will decrease, II and III will increase What is the correct set of quantum numbers for the highest energy electron of yttrium, 39Y? (A) 4, 1, 0, ½ (B) 4, 2, -1, ½ (C) 4, 0, 0, -½ (D) 3, 2, -2, ½ (E) 5, 2, 1, ½ 17. Which series is ranked in order of increasing electronegativity? (A) O, S, Se, Te (B) Cl, S, P, Si (C) In, Sn, N, O (D) C, Si, P, Se (E) Kr, Nr, Ne, He 18. In any one period of the periodic table, the element in Group IA, as compared to the element in GroupVIIA, has (A) a larger number of valence electrons. (B) a lower (less negative) electron affinity. (C) a smaller radius. (D) a higher ionization energy. (E) none of the above. 19. Which of the following would have the largest second ionization energy? (A) K (B) Ne (C) Cl (D) Na (E) Mg 20. Which of the following atoms releases the most energy when it adds an electron? (A) Si (B) P (C) S (D) Ge (E) As 21. Which element in the following pairs has the higher first ionization energy? a. F or O b. Al or Mg c. Zn or Ga d. Xe or Kr

3 22. Nitrogen has a higher first ionization energy than oxygen. This is principally the result of (A) a nuclear charge effect. (B) greater penetration of the nitrogen p orbitals. (C) a crowding effect of the electrons. (D) the extra neutrons of oxygen. (E) the half-filled subshell of nitrogen. The following figure shows electron affinities for the first 20 elements. 26. Assume that an element has the following ionization energies: First: 600 kj/mol Second: 1,800 kj/mol Third: 2,750 kj/mol Fourth: 11,600 kj/mol Fifth: 15,000 kj/mol Which of the following is the most probable electron configuration for this element? (A) 1s 2 2s 2 2p 6 (B) 1s 2 2s 2 2p 6 3s 2 (C) 1s 2 2s 2 2p 6 3s 1 (D) 1s 2 2s 2 2p 6 3s 2 3p 1 (E) 1s 2 2s 2 2p 6 3s 2 3p Which of the following electronic configurations would represent an atom with the least negative electron affinity? (A) ns 2 np 1 (B) ns 2 np 2 (C) ns 2 (D) ns 2 np 4 (E) ns 2 np Explain why beryllium has a more positive electron affinity than lithium. 24. Explain why chlorine has a greater negative electron affinity than sulfur. 28. In row 3 of the Periodic Table, which element has the lowest first ionization energy? 29. In row 3 of the Periodic Table, which element has the highest first ionization energy? 30. Of all the elements, which one has the highest first ionization energy? 31. What is the element that has the lowest first ionization energy? 32. What is the element with the greatest electronegativity? 25. Explain why phosphorous has a lower (less negative) electron affinity than silicon. 33. In row 2, which element has the smallest atomic radius? 34. Which element has the valence configuration 6s 2 6p 2? 3

4 35. Which element has the valence configuration 5s 2 5p 3? 36. Given the valence electron configuration of elements A, B, C, D and E, which element has the lowest first ionization energy? (A) 4s 1 (B) 5s 1 (C) 5s 2 (D) 5s 2 5p 1 (E) 5s 2 5p Predict the formula of a compound containing a. Ga and O b. Sc and Cl 40. Explain each of the following observations using principles of atomic structure and/or bonding. a. Potassium has a lower first-ionization energy than lithium. b. The ionic radius of N 3 is larger than that of O 2. c. A calcium atom is larger than a zinc atom. c. Ra and O 38. Use the Periodic Table to compare the elements O, F, and Na with respect to a. Atomic radius d. Boron has a lower first-ionization energy than beryllium. b. Ionization energy 39. The electron affinities of F and of the O ion are given below: F(g) + e F (g) H = -332 kj/mol O (g) + e O 2 (g) H = +710 kj/mol What is the essential difference in these two processes, and how does it account for the difference in the two energy changes? 41. Consider the following melting points in degrees Celsius: Alkali metals Halogens Li 181 F Na 98 Cl K 63 Br 2 7 Rb 39 I Cs 29 a. Account for the trend in the melting points of the alkali metals. b. Account for the trend in the melting points of the halogens. 4

5 42. Explain, in terms of electron configurations, orbital diagrams or shielding, why a. the atomic radius of sodium is smaller than that of potassium. b. bromine and iodine have similar chemical properties. 43. Explain, in terms of electron configurations, orbital diagrams, or shielding, why a. in the Periodic Table hydrogen can be placed in either Group 1A or 7A. b. the ionization energy of Ca + is greater than that of K even though they both have 19 electrons. c. Na has a relatively simple atomic spectrum while Cr has a very complex one. 44. Account for each of the following in terms of principles of atomic structure, including the number, properties, and arrangements of subatomic particles. a. The second ionization energy of sodium is about three times greater than the second ionization energy of magnesium. b. Phosphorus forms the fluorides PF 3 and PF 5, whereas nitrogen forms only NF Rank, from least to greatest, the following groups according to the ability of elements within the group to conduct electricity: metals, metalloids, nonmetals. 5

6 46. A 1.0 g sample of solid silver acetate (AgCH 3 CO 2 ) is added to 150 ml of a M sodium sulfide (Na 2 S) solution. Assume no change in volume of the solution when the solid is added. a. Write the balanced chemical equation, the full ionic equation and the net ionic equation for this reaction. Include states in the equations. Consider silver acetate to be dissolved and not a solid. b. Calculate the number moles of the silver acetate and sodium sulfide reactants. c. Identify the limiting reactant. Justify your choice with calculations. d. Calculate the concentrations of all species remaining in solution when the reaction is complete. e. Identify any spectator ions. Justify your choice. 6