3. INTRODUCTION
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The 20 industrial chemicals produced in greatest amounts in
the United States are main group elements or compounds, and
eight of the top ten may be classified as "inorganic"; numerous
other compounds of these elements are of great commercial
importance
Provides examples in which modern chemistry has developed
in ways surprisingly different from previously held ideas
6. COURSE MATERIAL
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The chemical properties of the
metallic elements can be
considered as arising from the
ability of the elements to lose
electrons to form the electron
sea that binds together the
cations and accounts for metallic
bonding
Consequently, elements with low ionization energies are likely to be metals and those with high
ionization energies are likely to be nonmetals. Thus, as ionization energies decrease down a group the
elements become more metallic, and as the ionization energies increase across a row the elements
become less metallic
11. THE 13 METAL
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The Group 15 elements—nitrogen, phosphorus, arsenic, antimony, and bismuth—are some of the most
important elements for life, geology, and industry. They range from gaseous nitrogen to metallic bismuth. The
members of this group, the ‘nitrogen group’, are sometimes referred to collectively as the pnictogens (from the
Greek for to stifle, a property of nitrogen). This name is neither widely used nor officially sanctioned. As in the
rest of the p block, the element at the head of Group 15, nitrogen, differs significantly from its congeners. Its
coordination number is generally lower and it is the only member of the group to exist as a gaseous, diatomic
13. OXYGEN, SULPHUR AND
SELENIUM
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Oxygen, sulfur, and selenium are
nonmetals, tellurium is a metalloid,
and polonium is a metal. Allotropy
and polymorphism are important
features of Group 16 and sulfur
occurs in more natural allotropes and
polymorphs than any other element.
The group electron configuration of
ns2np4 suggests a group maximum
oxidation number of +6. Oxygen
never achieves this maximum
oxidation state, although the other
elements do in some circumstances.
The electron configuration also
suggests that stability may be
achieved with an oxidation number
of +2, which is overwhelmingly
common for O. The most remarkable
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The striking difference between O-O and S-S single bond energies has important
consequences. The O-O bond enthalpy is 146 kJ mol-1 and peroxides are powerful oxidizing
agents: in contrast, the SS bond enthalpy of 265 kJ mol-1 is so high that it is used in biology to
stabilize protein structure by forming permanent linkages (RS-SR) between cysteine residues on
different protein strands and different regions of one strand.
15. HALOGEN
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The Group 17 elements, fluorine, chlorine, bromine, iodine, and astatine, are known as the halogens
from the Greek for ‘salt giver’. Fluorine and chlorine are poisonous gases, bromine is a toxic, volatile
liquid, and iodine is a sublimable solid. They are among the most reactive nonmetallic elements.
17. THE NOBLE GASES
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During a solar eclipse in 1868, a new emission
line, matching no known element, was found in
the spectrum of the solar corona. J. N. Locklear
and E. Frankland proposed the existence of a
new element named, appropriately, helium
(Greek, helios, sun). The same spectral line was
subsequently observed in the gases of Mount
Vesuvius.
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The properties of He deserve special note; it can diffuse through rubber and most glasses.
Below 2.18 K, ordinary liquid 4He (but not 3He) is transformed into liquid He(II) which has the
remarkable properties of a thermal conductivity 600 times that of copper, and a viscosity
approaching zero; it forms films only a few hundred atoms thick which flow up and over the side
of the containing vessel.
