Answers to UNIT 4'02 Self Test:

Part 1: Multiple Choice with Explanation

1.  (a) These elements contain 1 valence electron, which they lose in a chemical reaction.

2.  (c) Mn is a metal so it forms a cation.  Furthermore, since the net charge of the compound is zero and each O has a 2- charge, Mn must be +4 to cancel these out.

3.  (b) Carbon is a non-metal.  Non-metals make molecules.

4.  (a) Fluorine has 7 valence electrons and shares only one pair to attain an octet.

5.  (d) This is called the octet rule.

6.  (b) This compound is composed of only non-metals.

7.  (c) These are the electrons which occupy the outermost energy level.

8.  (c) The electronegativity difference is between .4 and 2.0 and the bond is between two non-metals..

9.  (a) This is a bond between a metal and a non-metal.  Also the electronegativity difference is greater than 2.0.

10. (c) This has polar bonds and bent geometry.

Part 2: Matching

18.  (bc)    19. (e)    20. (d)    21. (a)    22. (ac)    23. (b)    24. (ad)    25. (ab)    26. (be)    27. (ae)    28. (c)    29. (bd)

Part 3: Problems and Questions

30. +1    31. cations    32. manganese (III) oxide    33. ammonia    34. -ide    35. prefixes    36. oxygen

37.  K  4s¹   3s² 3p⁶     K⁺   cation
        N    2s² 2p³  2s² 2p⁶     N^3-   anion
        Ba   6s²  5s² 5p⁶     Ba²⁺   cation
        Br    4s² 4p⁵  4s² 4p⁶     Br^-   anion

38.  (a) Fe(ClO₂)₃  iron(III) chlorite    (b) Ba(C₂H₃O₂)₂  barium acetate    (c) SnCl₄  tin(IV) chloride

40.  (a) Mg₃P₂   (b) SnO₂   (c) KNO₃   (d) P₂O₃   (e) CCl₄   (f) H₂CO₃

41.  (a) barium chloride    (b) potassium bromide    (c) barium sulfate    (d) ammonium chloride    (e) phosphorus trichloride    (f) hydrosulfuric acid    (g) phosphoric acid    (h) iron(III) carbonate

42.  (a) CO₂   (b) CCl₄   (c) H₂O    (d) NH₃

43.  [For the Lewis Structure see the classroom bulletin board.] (a) bent; yes    (b) linear, yes    (c) tetrahedral    (d) linear, no    (e) pyramidal, no

44.  In a covalent bond the electrons are shared between the two bonding atoms.  In ionic bonding the electrons are exchanged.  An ionic bond is held together by attraction of oppositely charged ions, which are the result of the exchanged electrons.  In either case the elements in the bond attempt to achieve the same number of valence electrons as a noble gas.  This is called the "Octet Rule."  The measure of whether the electrons are transferred or shared in the bond depends on the difference in the electronegativity of the two elements which bond together.  In general, when a metal reacts with a non-metal the electronegativities are different enough that the electrons are given by the metal and accepted by the non-metal.  When non-metals combine their electronegativities are close to the same.  Therefore, the electrons are not lost but shared.  The electronegativity (e.n.) difference for determining whether the bond is covalent or ionic is as follows.  When the e.n. difference is less than 2.0 the bond is said to be covalent.  If the e.n. difference is greater than 2.0 then the bond is ionic.  Molecular compounds are distinguished by their low melting points, non-conductivity of electricity and that they form molecules.  Ionic compounds, however, have high melting points, form crystal lattice structures composed of formula units.  They are conductors of electricity when they are dissolved in water or in the melted state.  As solids they are brittle.

45.  Molecular compounds can be differentiated from ionic compounds in terms of their properties and formulas.  Molecular compounds are distinguished by their low melting points, non-conductivity of electricity and that they form molecules.  Ionic compounds, however, have high melting points, form crystal lattice structures composed of formula units.  They are conductors of electricity when they are dissolved in water or in the melted state.  As solids they are brittle.  In terms of their formulas, ionic compounds are formed between a metal and a non-metal while molecular compounds are formed between two non-metals.