Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 110

General Chemistry

Summer 2006

Lecture Notes::Lec 23_3 July

© R. Paselk 2006
 
     
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The Chemistry of the Elements

The Transition Metals

The transition elements have typical metallic properties: high reflectivity, a metallic luster, good electrical conductivity, and good thermal conductivity.

Note the electronic structures of the transition elements going across the periods (see chart below). Note the break in pattern at the 4th and 9th elements in the first and second series due to filling of d subshell (symmetry). This effect breaks down in the third series as the s and d subshells get closer due to the inner f subshells and relativistic effects.

On the other hand they exhibit a wide variation in

The transition metals tend to be quite similar across Periods as well as within Groups in Chemical properties.

 
Periodic Table of the Elements -Transition Metals
IIIB IVB VB VI VIIB VIIIB IB IIB
21Sc
4s23d1
E°=-2.08V*
 
3**
22Ti
4s23d2
E°=-1.63V
(2)
3
23V
4s23d3
E°=-1.2V
2
3
4
5
24Cr
4s13d5
E°=-0.74V
2
3
(4)
 
6
25Mn
4s23d5
E°=-1.18V
2
(3)
4
 
(6)
7
26Fe
4s23d6
E°=-0.45V
2
3
(4)
 
(6)
27Co
4s23d7
E°=-0.28V
2
3
28Ni
4s23d8
E°=-0.26V
2
(3)
29Cu
4s13d10
E°=+0.34V
(1), 2
30Zn
4s23d10
E°=-0.76V
2
 Y Zr Nb
Mo
5s14d5
Tc
 
E°=+0.4V
Ru
 
E°=+0.5V
Rh
 
E°=+0.6V
Pd
5s04d10
E°=+1.2V
 Ag
5s14d10
E°=+0.80V
 Cd
Lu  Hf Ta
 W
6s24d4
Re
Os
 
E°=+0.9V
Ir
 
E°=+1.0V
 Pt
6s14d9
E°=+1.2V
Au
6s14d10
E°=+1.7V
 Hg
 
E°=+0.80V
* Reduction potentials from M+2 (or M+3 for Sc & Cr) to the metal.
** Common oxidation states (less common in parenthesis).

The reactivities of the transition metals varies significantly for both chemical and physical reasons, e.g.:

Coordination Compounds

Complex ions are particularly common in the transition metals. When a complex ion is combined with a counter ion the result is a coordination compound. Note that complex ions can be both cations and anions, and a compound could be made up from two different complex ions.

When dealing with complex ions and coordination compounds one of the first things we need to be concerned with is nomenclature - how do we know what someone is talking about, and how do we describe a compound of interest?

Nomenclature of Complex Ions: Note that we still write, in formulae and names, the cation first and the anion second. The question then is how do we name the components of the complex ions themselves:

Anion Name Ligand Name
Cl- chloride -Cl chloro
I- iodide -I iodo
CN- cyanide -CN cyano
OH- hydroxide -OH hydroxo

Anion Name Ligand Name
SO42- sulfate -OSO3 sulfato
C2O42- oxalate -O(CO)2O- oxalato

Anion Name Ligand Name
SCN- thiocyanate -SCN thiocyanato
    -NCS isothiocyanato
NO2- nitrite -NO2 nitro
    -ONO nitrito

Molecule Name Ligand Name
H2O water -OH2 aqua (old = aquo)
NH3 ammonia -NH3 amine
CO carbon monoxide -CO carbonyl

Examples

Formula Name
[Cr(H2O)6]3+ Hexaaquachromium(III) ion
[CoCl4(NH3)2]- Diamminetetrachlorocobaltate(III) ion
[Cr(OH)2(H2O)4][FeCl2(CN)2(NH3)2] Tetraaquadihydroxychromium(III) diamminedichlorodicyanoferrate(III)*
* I don't know if this compound actually exists, but for nomenclature examples I refuse to be constrained by reality!

Stereoisomerism

When a number of different ligands bind to a single central atom their arrangement may result in sterioisomerism - the situation where substances with the same bonds (e.g. same Lewis Structures) are different species because of differing spatial arrangements of bonds around the central atom. Isomerism is extraordinarily important in biology and organic chemistry. Here we'll look at complex ion examples.

The stereoisomerism of complex ions can be organized by coordination number, with the most important coordination numbers for stereoisomers being 2, 4, and 6.


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Last modified 3 July 2006