162
Chemical Oceanography, 4th Edition
The classification of metals made by Goldberg (1965) can be expanded using the Pearson
division of solutes into hard and soft acids (see Table 4.5).
When using the ion- pairing model, the activity of the free ion i is given by
a i = [i] F γ F (i)
(4.58)
where [i] F is the molal concentration, and γ F (i) is the activity coefficient of the free or uncomplexed ion. This value of γ F is assumed to be only a function of the ionic strength and independent of the relative composition. Since the activity coefficient of the ion is also related
to the total concentration and activity coefficient by
a i = [i] T γ T (i)
(4.59)
the total or stoichiometric activity coefficient is given by
Filterable
Membrane filterable
Dialyzable
In solution
Free
Metal
Ions
Inorganic ion
pairs & complexes
Organic complexes
& Chelates
Metal species
bound to high
mol. wgt. org.
Metal in
colloids
Metals on
colloids
Ppts., Org.
particles
Diameter Range:
10 Å
100 Å
1000 Å
Examples :
Mg 2+
Cu
2+
Fe
3+
CuCO 3
Fe(OH) 2
CdCl
+
Me-SR
Me-OOCR
Me-fulvics
Me on
Humic
Material
Me(OH) x
Me on
BaSO 4 (s)
clays
CaCO 3 (s)
Proteins
FeOOH
Fe(OH) 3
MnOx
FeOOH
on oxides
Figure 4.30
The various forms of elements in natural waters. Ppts. = parts per thousand.
Table 4.5
Division of Solutes into Hard and Soft Acids
Hard Acids
Borderline
Soft Acids
All A- metal cations plus Cr 3+ , Mn 3+ ,
Fe 3+ , Co 3+ , Bi 3+ , UO 2+ , VO 2+
All bivalent transition metal
cations plus Zn 2+ , Pb 2+ , Bi 3+
All B- metal cations minus Zn 2+ ,
Pb 2+
Also species like BF 3 , BCl 3 , SO 3 , RSO 2+ ,
RPO 2+ , CO 2 , RCO+, R 3 C+
SO 2 , NO+, B(CH 3 ) 3
All metal atoms, bulk metals, I 2 ,
Br 2 , ICN, I+, Br+
Class A metals: Cations are all those with an electronic configuration of noble gases (H+, Li+, Na+, K+,
Rb+, Cs+, Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Al 3+, Sc 3+ , La 3+ , Si 4+ , Ti 4+ , Zr 4+ , Th 4+ )
Transition metals: Cations with 1–9 outer- shell electrons (V 2+ , Cr 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Ti 3+ , V 3+ ,
Cr 3+ , Mn 3+ , Fe 3+ , Co 3+ )
Class B metals: Cations with electron numbers 10 or 12 (Cu+, Ag+, Au+, Tl+, Ga+, Zn 2+ , Cd 2+ , Hg 2+ ,
Pb 2+ , Sn 2+ , Tl 3+ , Au 3+ , In 3+ , Bi 3+ )
Chemical Oceanography, 4th Edition
The classification of metals made by Goldberg (1965) can be expanded using the Pearson
division of solutes into hard and soft acids (see Table 4.5).
When using the ion- pairing model, the activity of the free ion i is given by
a i = [i] F γ F (i)
(4.58)
where [i] F is the molal concentration, and γ F (i) is the activity coefficient of the free or uncomplexed ion. This value of γ F is assumed to be only a function of the ionic strength and independent of the relative composition. Since the activity coefficient of the ion is also related
to the total concentration and activity coefficient by
a i = [i] T γ T (i)
(4.59)
the total or stoichiometric activity coefficient is given by
Filterable
Membrane filterable
Dialyzable
In solution
Free
Metal
Ions
Inorganic ion
pairs & complexes
Organic complexes
& Chelates
Metal species
bound to high
mol. wgt. org.
Metal in
colloids
Metals on
colloids
Ppts., Org.
particles
Diameter Range:
10 Å
100 Å
1000 Å
Examples :
Mg 2+
Cu
2+
Fe
3+
CuCO 3
Fe(OH) 2
CdCl
+
Me-SR
Me-OOCR
Me-fulvics
Me on
Humic
Material
Me(OH) x
Me on
BaSO 4 (s)
clays
CaCO 3 (s)
Proteins
FeOOH
Fe(OH) 3
MnOx
FeOOH
on oxides
Figure 4.30
The various forms of elements in natural waters. Ppts. = parts per thousand.
Table 4.5
Division of Solutes into Hard and Soft Acids
Hard Acids
Borderline
Soft Acids
All A- metal cations plus Cr 3+ , Mn 3+ ,
Fe 3+ , Co 3+ , Bi 3+ , UO 2+ , VO 2+
All bivalent transition metal
cations plus Zn 2+ , Pb 2+ , Bi 3+
All B- metal cations minus Zn 2+ ,
Pb 2+
Also species like BF 3 , BCl 3 , SO 3 , RSO 2+ ,
RPO 2+ , CO 2 , RCO+, R 3 C+
SO 2 , NO+, B(CH 3 ) 3
All metal atoms, bulk metals, I 2 ,
Br 2 , ICN, I+, Br+
Class A metals: Cations are all those with an electronic configuration of noble gases (H+, Li+, Na+, K+,
Rb+, Cs+, Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Al 3+, Sc 3+ , La 3+ , Si 4+ , Ti 4+ , Zr 4+ , Th 4+ )
Transition metals: Cations with 1–9 outer- shell electrons (V 2+ , Cr 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Ti 3+ , V 3+ ,
Cr 3+ , Mn 3+ , Fe 3+ , Co 3+ )
Class B metals: Cations with electron numbers 10 or 12 (Cu+, Ag+, Au+, Tl+, Ga+, Zn 2+ , Cd 2+ , Hg 2+ ,
Pb 2+ , Sn 2+ , Tl 3+ , Au 3+ , In 3+ , Bi 3+ )