the production of thymoquinone from thymol and carvacrol

CHAPTER 3
TRANSITION METALS AND COORDINATION
CHEMISTRY
3.1. Definition and Physical Properties of Transition Metals
The transition metals constitute groups 3 through 12 of the periodic table.
They’re the elements which have partially filled d-shells and Zn, Cd and Hg are
included even though their d-shells are entirely filled. The first row transition metals
have the electronic configuration [Ar] 3d n 4s m where n is between1-10 and m is
between1-2. The second row has the configuration [Kr] 4d 5s, and the third row have
the configuration [Xe] 5d 6s (Solomons 1988).
IIIB, IVB, VB, VIB, VIIB, VIII, IB, IIB elements of the periodic table are the
transition metals that are the most concern. As with all metals, the transition elements
are both ductile and malleable, and conduct electricity and heat. Similarities occur
within a period as well as within a group due to last electrons (Solomons 1988).
The elements in the periodic table as shown in Figure 3.1 are often divided into
four categories: (1) main group elements, (2) transition metals, (3) lanthanides, and (4)
actinides. The main group elements include the active metals in the two columns on the
extreme left of the periodic table and the metals, semimetals, and nonmetals in the six
columns on the far right. The transition metals are the metallic elements that serve as a
bridge, or transition, between the two sides of the table. The lanthanides and the
actinides (f block elements) at the bottom of the table are sometimes known as the inner
transition metals because they have atomic numbers that fall between the first and
second elements in the last two rows of the transition metals. f-block elements are not
traditionally treated as transition elements since f electrons do not affect bonding.
Transition metals are more electronegative than the main group metals; therefore they
are more likely to form covalent compounds (Morrison 1992).
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