Big Idea: The following list is a GUIDE to what you should study in order to be prepared for the Unit #4 Test on Chemical Bonding.

Transcription

1 4 Chemical Bonding Learning Goals Big Idea: The following list is a GUIDE to what you should study in order to be prepared for the Unit #4 Test on Chemical Bonding. Goals: The student will be able to identify why elements are electrically unstable or stable recall how elements achieve stability define valence electron, ionic bond, covalent bond, metallic bond, electronegativity, octet rule, molecule, ion, intermolecular force draw lewis dot symbols recall the general properties for ionic compounds, metals, and molecular compounds Identify the ion that representative elements will make based on their location on the periodic table distinguish between monatomic and polyatomic ions distinguish between cations and anions predict the type of bonding that will take place between atoms justify why a particular type of bonding will take place between two atoms distinguish between strong/weak and nonelectrolytes based on percent dissociation and conductivity conceptually compare lattice energy of two ionic compounds based on strength of force of attraction (coulomb s law) convert between names and formulas of ionic compounds convert between names and formulas of binary molecular compounds recall the three types of covalent bonds and identify their relative length, strength, and number of shared pairs of electrons predict the polarity of a covalent bond (polar vs nonpolar) draw and identify an individual bond moment draw the lewis structure for a molecule (molecular compound) distinguish between bonding and nonbonding electrons calculate the formal charge of an element within a molecule identify if a molecule has resonance draw resonance for relevant molecules identify exceptions to the octet rule (incomplete/expanded octet) identify and draw the molecular geometry of a molecule (VSEPR theory) identify the bond angle for a molecule predict the polarity of a molecule (polar/nonpolar) predict the type of intermolecular force between molecules predict if a molecule can hydrogen bond with itself or another substance Additional Problems: 1. Determine the number of protons and electrons for the following ions: a. P 3 c. F e 3+ e. S 2 b. T i 4+ d. Mn 2+ 1

2 2. Which of the following compounds are likely to be ionic? Which are likely to be molecular?, LiF, BaCl, B H, KCl, C H, NaBr, BaF, CCl, ICl, CsCl, NF SiCl Write the formula for the following ionic compounds: a. magnesium nitride d. mercury(i) nitrite b. chromium(iii) sulfate e. cesium sulfide c. titanium(iv) oxide f. calcium phosphate g. rubidium sulfate h. barium hydride* i. sodium oxide 4. Write the chemical formulas for the following molecular compounds: a. carbon disulfide e. iodine heptafluoride b. disilicon hexabromide f. boron trichloride c. sulfur tetrafluoride g. tetraphosphorus decasulfide d. dinitrogen pentoxide h. selenium hexafluoride 5. Match each of the diagrams shown here with the following ionic compounds: O, LiH, Na S, Mg(NO ) (green spheres represent cations and red spheres represent anions) Al Name the following ionic compounds: a. Cu(NO 3 b. KH 2 P O 4 c. ClO NH 4 3 d. V 2 O 5 e. Li 2 SO 3 f. CrO Na 2 4 g. H Br h. Al(OH) 3 7. Name the following molecular compounds: a. SiCl 4 d. O b. P 4 O 10 e. P F 3 c. NF 3 f. P F 5 Cl 2 7 g. P 4 O 6 8. Each of the following pairs of elements will react to form an ionic compound. Write the formulas and name these compounds: a. barium and oxygen c. aluminum and sulfur b. calcium and phosphorus d. lithium and nitrogen 9. What is wrong with the chemical formula for each of the following compounds: a. magnesium iodate, Mg(IO 4 b. barium sulfite, B as c. ammonium bicarbonate, HCO NH What is wrong with the name (in parentheses) for each of the following compounds: a. SnCl 4 (tin chloride) b. Cu 2 O (copper(ii) oxide) c. Co(NO 3 (cobalt nitrate) d. Cr O (sodium chromate) Na

3 11. Which elements are most likely to form ionic compounds? Which metallic elements are most likely to form cations with different charges? 12. Explain how ionization energy and electron affinity determine whether atoms of elements will combine to form ionic compounds. 13. In which of the following states would NaCl be electrically conducting? Explain your answers. a. Solid b. Molten (that is, melted) c. Dissolved in water 14. Beryllium forms a compound with chlorine that has the empirical formula BeCl 2. How would you determine whether it is an ionic compound? (The compound is not soluble in water.) 15. Draw lewis dot symbols for the following atoms and ions: a. Li +, Li b. Cl, Cl c. S 2, S d. P b 2+, P b 16. Use lewis dot symbols to show the formation of the following a. aluminum oxide b. barium hydride c. aluminum nitride 17. Specify which compound in the following pairs of ionic compounds has the higher lattice energy: (explain your choice) a. LiCl or CsBr c. LiF or LiBr b. KCl or MgO d. Mg 3 N 2 or NaCl 18. An ionic bond is formed between a cation and an anion. How would the energy of the ionic bond be affected by the following changes? a. Doubling the radius of A + b. Tripling the charge on A + c. Doubling the charges on A + and B d. Decreasing the radii of A + and B to half their original values A Why is it not possible for hydrogen to form double or triple bonds in molecular compounds? 20.Classify the following bonds as ionic, polar covalent, or nonpolar covalent a. the CC bond in H 3 CCH 3 b. K I c. the NB bond in H 3 NBCl 3 d. CF 4 e. the SiSi bond in Cl 3 SiSiCl 3 f. the SiCl bond in Cl 3 SiSiCl 3 g. CaF 2 h. NH 3 B 3

4 21. Draw the lewis structure for the following: a. carbon disulfide h. N 2 F 2 b. formic acid (HCOOH) i. Si 2 c. nitrite ion j. OH d. BF 2 k. CH 2 ClCOO e. AsF + 5 l. CH 3 NH 3 f. SF 4 m. P H 3 g. OF 2 n. H 2 S o. N 2 H 4 p. HClO 3 q. COBr 2 r. BeCl 2 s. XeF 2 t. XeF 4 u. XeF Draw the lewis structure and show formal charges for the nitrite, peroxide, and ammonium ions. 23. Draw the most reasonable Lewis structure of a molecule that contains a N atom, a C atom, and a H atom. 24.Draw three resonance structures for the thiocyanate ion, order of importance. SCN. Rank the structures in decreasing 25. Draw reasonable Lewis structure s of sulfuric acid (H 2 SO 4 ). 26. How many lone pairs are on the underlined atoms in these compounds? a. H Br b. H 2 S c. C H List the following bonds in order of increasing ionic character: a. carbon to hydrogen, c. bromine to hydrogen b. fluorine to hydrogen d. sodium to chlorine e. potassium to fluorine f. lithium to chlorine 28. The following Lewis structures for (a) HCN (b) C 2 H 2 (c) SnO 2 (d) BF 3 (e) HOF and (g) NF 3 are incorrect. Explain what is wrong with each one and give a correct structure for the molecule. (Relative positions of atoms are shown correctly.) 29. Draw three resonance structures for the following: (show formal charges) a. ClO 3 b. HN 3 (HNNN) c. OCN 30. Why does the octet rule not hold for many compounds containing elements in the third period of the periodic table and beyond? 31. Identify the molecular geometry and polarity for all molecules in #21 above (skip letters s, t, and u) 4

5 32. Name the type(s) of intermolecular forces that exist between molecules (or basic units) in each of the following species: a. LiF d. benzene ( C 6 ) g. NaCl b. CH 4 e. CH 3 Cl h. CS 2 c. SO 2 f. P F Which of the following species are capable of hydrogen bonding among themselves? a. H 2 S c. CH 3 OH f. BeH 2 b. C 6 d. H I g. CH 3 COOH e. KF 34. Explain the term polarizability. What kind of molecules tend to have high polarizabilities? What is the relationship between polarizability and intermolecular forces? 35. Explain the difference between a temporary dipole moment and the permanent dipole moment. 36. The compounds Br 2 and ICl have the same number of electrons, yet Br 2 melts at 7.2 C and melts at 27.2 C. Explain. 37. If you lived in Alaska, which of the following natural gases would you keep in an outdoor storage tank in winter? Explain why. methane (CH 4 ), propane (C 3 H 8 ), or butane (C 4 H 10 ) *Challenge but you can do it! 38. Arrange the following in order of increasing boiling point: RbF, CO 2, CH3 OH, CH3 Br. Explain your reasoning. 39. Diethyl ether has a boiling point of 34.5 C, and 1-butanol has a boiling point of 117 C : I Cl Both of these compounds have the same numbers and types of atoms. Explain the difference in their boiling points. 40.What kind of attractive forces must be overcome in order to a. Melt ice b. Boil molecular bromine c. Melt solid iodine d. Dissociate F 2 into F atoms? 5