Page 90 - Theory and Problems of BEGINNING CHEMISTRY

CHAP. 5] CHEMICAL BONDING 79

5.16. What is the formula of the compound of (a) magnesium and nitrogen? (b) lead and oxygen?
Ans. (a)Mg 3 N 2 . Magnesium has two electrons in the valence shell of each atom, and nitrogen requires three.
(b) PbO 2 . This problem involves the same reasoning as the prior problem.

5.17. Arrange the electrons in each of the following ions in shells: (a)K ,(b)Mg , and (c)N .
+
2+
3−
Ans. Shell Number
Ion 1 2 3 4
(a)K + 2 8 8 0
(b)Mg 2+ 2 8 0
(c) N 3− 2 8

5.18. Write formulas for the compounds formed by the reaction of (a) magnesium and nitrogen, (b) barium
and bromine, (c) lithium and nitrogen, (d) sodium and sulfur, (e) magnesium and sulfur, ( f ) aluminum
and fluorine, and (g) aluminum and oxygen.
Ans. (a)Mg 3 N 2 (b) BaBr 2 (c)Li 3 N(d)Na 2 S(e) MgS ( f ) AlF 3 (g)Al 2 O 3

5.19. What ions are present in each of the following compounds: (a) MnCl 2 ,(b)Cu 2 S, (c) CuO, (d) Ba(ClO 4 ) 2 ,
(e) (NH 4 ) 2 SO 4 , and ( f ) MgCO 3 ?
Ans. (a)Mn 2+ and Cl − (b)Cu and S 2− (c)Cu 2+ and O 2− (d)Ba 2+ and ClO 4 − (e)NH 4 and SO 4 2−
+
+
( f )Mg 2+ and CO 3 2−
With binary compounds of transition metals, determine the charge on the anion first and make the cation
balance that charge.
5.20. Write formulas for the compounds formed by the following pairs of ions: (a)Li and Cl ,(b)Pb 4+ and
+
−
O ,(c)K and S ,(d)Al 3+ and S ,(e)Mg 2+ and N , and ( f )Co 2+ and ClO .
2−
2−
3−
2−
−
+
Ans. (a) LiCl (b) PbO 2 (c)K 2 S(d)Al 2 S 3 (e)Mg 3 N 2 ( f ) Co(ClO) 2
−
−
+
5.21. Write the formulas for the compounds of (a)Ca 2+ and ClO and (b)K and ClO 2 . Explain why one
of the formulas requires parentheses.
−
Ans. Ca(ClO) 2 and KClO 2 . The parentheses mean two ClO ions; no parentheses mean two O atoms in one ClO 2 −
ion.
5.22. Complete the following table by writing the formula of the compound formed by the cation at the left
and the anion at the top. NH 4 Br is given as an example.
Br − NO 2 − NO 3 − SO 4 2− PO 4 3−
+ NH 4 Br
NH 4
Li +
Mn 2+
Fe 3+
Ans. Br − NO 2 − NO 3 − SO 4 2− PO 4 3−

+ NH 4 Br
NH 4 NH 4 NO 2 NH 4 NO 3 (NH 4 ) 2 SO 4 (NH 4 ) 3 PO 4
Li + LiBr LiNO 2 LiNO 3 Li 2 SO 4 Li 3 PO 4
Mn 2+ MnBr 2 Mn(NO 2 ) 2 Mn(NO 3 ) 2 MnSO 4 Mn 3 (PO 4 ) 2
Fe 3+ FeBr 3 Fe(NO 2 ) 3 Fe(NO 3 ) 3 Fe 2 (SO 4 ) 3 FePO 4