Chemistry Reference
In-Depth Information
electropositive character than the s-block metals. Gallium, indium, and thallium are
post-transitional metals, so their nuclear effective charges are higher than those of
boron and aluminum. Their first ionization energy is higher than that of aluminum.
Due to the very high ionization energies for Al
3+
, Ga
3+
, and In
3+
, the compounds
of these elements in the oxidation state +3 are mainly covalent, yet these ions are
formed easily in solution due to their high enthalpy of hydration.
Group 14 (IV A) (the carbon group) includes a nonmetal (carbon), silicon, and
germanium, which are metalloids (Si behaves as a nonmetal mostly, but Ge behaves
as a metal) and the typical metals, tin and lead. These elements have 4 electrons in
electrons are usually shared; silicon and germanium can form +4 ions, tin and lead
can form +2 ions, and only carbon can form −4 ions.
Group 15 (V A) (the nitrogen group) has an electronic configuration ns
2
np
3
, with
five valence electrons, three of which are unpaired electrons in the p subshell. These
are sometimes shared, in double or triple bonds of very stable compounds. Nitrogen
and phosphorus are nonmetals. The group includes two metalloids (As behaves as a
nonmetal mostly, while Sb as a metal), and one metal (Bi). The gradual variation of
the chemical character in the group is linked to the decrease of the energy of ioniza-
tion and to the increase of the atomic radii.
Similar to the other groups that have been presented,
group 16 (VI A)
(the chal-
cogens or
the oxygen family) starts with an element whose physical properties and
chemical reactivity do not resemble those of the rest of the group. Here also, the
metallic character increases down the group: oxygen and sulphur are nonmetals,
selenium and tellurium are considered metalloids (they are referred to as a metal
when in elemental form), while radioactive polonium is classified either as a post-
transitional metal or metalloid (Hawkes 2010; Bentor 2011).
The properties and behavior of p-block metals are less homogenous than those of
the s-metals because of their atomic and ionic sizes and other characteristics such as
their unusual crystalline structures and the presence of the pair of electrons on the s
orbital (s
2
) of the outermost electron shell. These s
2
orbital electrons do not partici-
pate in chemical interactions (covalent or ionic) (
inert electron pair
). This influence
increases with atomic number within a group.
The d-block is situated in the middle of the periodic table and includes groups 3 to
12 (III B, IV B, V B, VI B, VII B, VIII B, IX B, X B, I B, II B) (
Figure 2.2
)
. Within the
d-block there are metals known as
transition metals
or
transition elements
, and also
some post-transition metals (group 12). The term
post-transition metal
is sometimes
used to describe the elements that have metallic character and are situated at the right
of the transition elements.
The d-block transition metals/elements are considered those elements that have,
as their name suggests, the d-orbital subshells partly occupied in either the neutral
atom or ionic state (IUPAC 2004). Accordingly, the following metals can be included
in this group:
•
Copper, silver, and gold, which have a completely filled (n-1)d
10
ns
1
subshell
in atomic state, but have a partly filled d orbital in ionic state: Cu(II) 3d
9
,
Ag(II) 4d
9
and Au(III) 5d
8
.
