FREE ESSAY ON TRANSITION ELEMENTS

TRANSITION ELEMENTS

Transition Elements, series of chemical elements that share similar electron orbital
structures and hence similar chemical properties. The transition elements are commonly
defined as the 30 elements with atomic numbers 21 to 30, 39 to 48, and 71 to 80.
The transition elements exhibit multiple valences or oxidation states typically ranging
from +1 to +8 in compounds. In organometallic compounds, consisting of metals bonded to
organic species, transition metals sometimes take on negative oxidation states. The
transition elements have such typical metallic properties as malleability, ductility,
high conductivity of heat and electricity, and metallic luster. They tend to act as
reducing agents (donors of electrons), but are less active in this regard than the alkali
metals and alkaline earth metals, which have valences of +1 and +2, respectively. There
are exceptions, as in the case of mercury (Hg), which is a liquid Transition elements in
general have high densities and melting points and exhibit magnetic properties. They form
both ionic and covalent bonds with anions (negatively charged ions), and such compounds
are in general brightly colored.. They have high electrical conductivity because of
delocalization of the s electrons similar to what occurs in the alkali and alkaline-earth
metals. Another characteristic of the transition metals is the great variety of oxidation
states shown in its compounds.
Several transition elements and their compounds are important catalysts (see Catalysis)
in a variety of industrial processes, especially in the manufacture of petroleum and
plastic products, where organic molecules are hydrogenated, oxidized, or polymerized (see
Chemical Reaction; Hydrogenation; Polymer). Compounds of titanium, aluminum, or chromium
are used in the polymerization of ethylene to form polyethylene. Catalysts containing
iron are used in preparing ammonia from hydrogen and nitrogen. Molecules containing
transition elements are important to the biochemical processes in many living systems,
the most familiar example of which is the iron-containing heme complex of hemoglobin,
which is responsible for oxygen transport in the blood of all vertebrates and some
invertebrates. Most transition metals are colored and make some of their ionic compounds
colored. This is because they absorb some of the frequencies of white light. This is
attributed to electronic transitions in the d subshell, separating them into different
levels of energy. When light is absorbed, an electron is raised from a lower state to a
higher state, giving the rise to color. The stored energy is then dissipated through
heat. 
The transition metals also have complex ionic structures because of the availability of d
orbitals for participating in chemical bonding.