ANSWER SOLUTION for PROBLEM SET #3

 (Specified page numbers are from the text Introduction to General, Organic, and Biological Chemistry. Matta, Wilbraham, and Stanley.)

 5.28    A metal (an element on the left of the periodic table) and a nonmetal (an element on the right side of the periodic table) react to form an ionic compound.     

         (a)    will not form an ionic compound; two nonmetals

(b)   will form an ionic compound; a metal and a nonmetal

(c)    will form an ionic compound; a metal and a nonmetal

(d)   will form an ionic compound; a metal and a nonmetal

5.32    Determine the number of ions needed of each anion and cation to equal a net charge of 0 and then write out the formula.  The formula is written with the cation first followed by the anion.  The number of ions needed will be the subscript number for the ion in the formula. (p118)

(a)    FeCl₂

(b) NH₄NO₃           

  (c) Al₂S₃

(d) Mg(OH)₂   

5.34.1    See Table 5.2, Table 5.3, Table 5.4 for common cation, anion and polyatomic anion  names.  Do you see a pattern for naming cations? anions?

(a)    K⁺, potassium ion; OH^-, hydroxide ion

(b)    Li⁺, lithium ion; CO, carbonate ion

(c)    Ag⁺, silver ion; NO₃^-, nitrate ion

(d)    Li⁺, lithium ion; Br^-, bromide ion

 5.44    Fluorine, chlorine, and bromine are all in Group 7A, and therefore all have 7 valence electrons.  Since electron dot structures show the number of valence electrons, the structures for the three elements are identical.

5.50 

(a)    NH₃

(b)   HCCl₃

(c)    HF

 (d)   C₂H₆

5.58    The most polar bond is the bond with the greatest electonegativity difference (Table 5.5; p.127-128).  Electronegativity is a measure of how much an element "likes" electrons.  If two elements are bonded together and have dissimilar electronegativities, the one with the higher electronegativity will garner the larger share of the electron bonding cloud.   This uneven sharing makes the bond "polar".  The larger the electronegativity difference, the more polar the bond.

 In order of decreasing polarity, the Electonegativity differences are as follows

5.62  There are four "things" attached to the ammonia molecule so the lone pair and three hydrogens take on a tetrahedral arrangement. 

In an ideal tetrahedron, the angles between bonds or between a bond and a lone pair would be 109.5^o.   The unshared pair of electrons repels the bonding electrons more so that the HNH bond angle is reduced to less than 109.5°.

 5.70