A. Names, symbols, and electronic configurations of the first transition series

 

Element	Symbol	Electronic Configuration
Scandium	Sc	[Ar]3d14s2
Titanium	Ti	[Ar]3d24s2
Vanadium	V	[Ar]3d34s2
Chromium	Cr	[Ar]3d54s1
Manganese	Mn	[Ar]3d54s2
Iron	Fe	[Ar]3d64s2
Cobalt	Co	[Ar]3d74s2
Nickel	Ni	[Ar]3d84s2
Copper	Cu	[Ar]3d104s1
Zinc	Zn	[Ar]3d104s2

Notes. There are anomalies in the electronic configurations at chromium and at copper. The configuration of copper is related to its chemistry; it is the only first transition series metal to have a relatively common +1 oxidation state.

Don't confuse manganese (atomic number 25) with magnesium (atomic number 12)!

A substance is said to be paramagnetic if it contains unpaired electrons, and diamagnetic if all electrons are paired. Most compounds between main group elements, including organic compounds, are diamagnetic. (There are a few exceptions, e.g. NO, NO₂, the superoxide ion O₂^-, and a few other species.)

On the other hand, a large number of compounds involving transition metals are paramagnetic with 1-5 unpaired electrons associated with each metal ion. The actual number of unpaired electrons can be determined with a Gouy balance. A Gouy balance is like a normal balance, but it has an electromagnet associated with it. A sample of compound is weighed with the magnet off, and again with the magnet on. A paramagnetic compound is attracted to the magnet with a force related to the number of unpaired electrons. Calibration with known paramagnetic substances allows a determination of the unpaired electrons in the sample.

Measurement of the magnetism of FeCl₃ shows that there are five unpaired electrons for each iron(III). This shows that the electronic configuration of iron(III) is [Ar]3d⁵, not [Ar]3d³4s². Thus the 4s electrons are removed before 3d electrons when transition metal ions are formed.
 
 

Notes. The most common oxidation state(s) for each element are shown in bold.

Note the symmetry about manganese. The maximum oxidation number increases by one from Sc through Mn, then decreases by 1 down to Zn.

The maximum oxidation number of the elements Sc through Mn corresponds to removal of all the 4s and 3d valence electrons.

Although iron does not have an oxidation number above +6, its congeners in the second and third transition series do. Both ruthenium (Ru) and osmium (Os) can achieve oxidation numbers of +8.

Compounds exist where the transition metal has a zero or even negative oxidation number. These include compounds involving benzene, carbon monoxide, organophosphines, and other ligands capable of pi-bonding. Examples include Cr(C₆H₆)₂, Fe(CO)₅, Mo(Me₃P)₆, Mn(CO)₅^-, and tens of thousands of other compounds.
 
 

See Kotz and Treichel (4th edition). Figures 23.7 (density), 23.8 (melting point), and 8.11 (atomic radii).

Or see Chang (6th edition). Figure 8.6 (atomic radii).

Transition metals that are essential for human health include V, Cr, Mn, Fe, Co, Cu, Zn, and Mo. The roles that vanadium and chromium play in glucose metabolism is still a research area, and the chromium-containing "glucose tolerance factor" has yet to be definitively characterized. Cobalt is essential, but only as its Vitamin B12 complex. There are hundreds of enzymes that contain iron, copper, and zinc, and iron is an essential constituent of myoglobin and hemoglobin used for oxygen storage and transport.
 
 

This page is http://chemiris.labs.brocku.ca/~chemweb/courses/chem232/CHEM2P32_Lecture_2.html
Created January 11, 2001 by M. F. Richardson
© Brock University, 2001