Chemistry Reference
In-Depth Information
+
potassium hydroxide (aq)
Iron hydroxide (s, green) + potassium nitrate (aq)
Iron nitrate (aq)
+
-
+
2
+
-
+
+
-
-
+
-
-
+
-
- -
2
+
2
+
-
-
-
-
+
+
2
+
- -
{(Fe
2+
)
2
(OH
-
)
4
} + 4 K
+
(aq) + 4 NO
3
-
(aq)
2 Fe
2+
(aq) + 4 NO
3
-
(aq) + 4 K
+
(aq) + 4 OH
-
(aq)
1 Fe
2+
(aq)
2 OH
-
(aq)
Fe(OH)
2
(s)
+
Fig. 10.22 Beaker model for the regrouping of ions in a precipitation reaction
Ag
þ
(aq)
Cl
ð
Cd
2
þ
(aq)
S
2
ð
þ
aq
Þ!
AgCl
ð
s
;
white
Þ
þ
aq
Þ!
CdS(s
;
yellow)
Ba
2
þ
(aq)
SO
4
2
ð
Ca
2
þ
(aq)
CO
3
2
ð
þ
aq
Þ!
BaSO
4
ð
s,white
Þ
þ
aq
Þ!
CaCO
3
ð
s
;
white
Þ
Hg
2
þ
(aq)
2I
ð
Fe
2
þ
(aq)
2OH
ð
þ
aq
Þ!
Hgl
2
ð
s, red
Þ
þ
aq
Þ!
Fe(OH
Þ
2
ð
s
;
green
Þ
Cu
2
þ
(aq)
S
2
ð
CuS (s, black) Fe
3
þ
(aq)
3OH
ð
þ
aq
Þ!
þ
aq
Þ!
Fe(OH
Þ
3
ð
s
;
brown
Þ
10.5.5 Combination of Nonmetal Atoms (“Right and Right
in Periodic Table”)
The combinations of nonmetal atoms lead to familiar molecules like CH
4
,NH
3
,
H
2
O, or HF and on the other side to giant structures like in crystals of diamond,
graphite, or silicon. In these cases directed bonding forces exist between the
nonmetal atoms, the concept of bonding valence sorts the bonding capacity of
atoms based on their position in the periodic table (see Fig.
10.23
): the C atom
bonds with four H atoms in the CH
4
molecule. Accordingly the C atom is tetrava-
lent, the N atom is trivalent, the O atom is bivalent, H or F atoms are monovalent. In
later conceptions of the nucleus-shell model of an atom, the bonding valence
corresponds to the number of bonding electron pairs or electron clouds.
The usual molecular model kits display the bonding valence: models for C atoms
have four push buttons, which point at the tetrahedral corners with an angle of 109
.
Models for N atoms have three push buttons, for O atoms they have two push
buttons etc. Since these molecular model kits are familiar, they will not be
explained any further. The question remains as to how experts determine the
structure of molecules and thereby bond length and bond angle. On the one hand
there are the methods of X-ray analysis, on the other hand there are spectroscopic
