3d block data notes:
Atomic and ionic radii are
quoted in pm (1 picometre, 10–12 m), 1000 pm = 1 nm (1 nanometre
= 10–9 m)
na means 'not applicable' or 'not available'.
The electronegativity values
are from the Pauling scale.
Redox potentials
See Appendix 11
Some 3d–block compounds, complexes, oxidation states
& electrode potentials
Ionic radii relate to the
'isolated' theoretical ion, NOT the hydrated aqueous ion.
Polarizing power is a measure of
the ions charge density which has important chemical consequences e.g.
the bonding nature of metals with non–metals
e.g. an ionic or a covalent MCln
and the acidity of the hydrated
aqueous ion [M(H2O)6]n+(aq)
which is capable of donating protons.
The ion charge divided by the
ionic radius of the 'isolated ion' is a 'reasonable' number scale for easy comparison
of polarising power, and in the tables I've multiplied the
charge/radius by 100 to make a suitable scale.
Obviously, the larger the charge,
or the smaller the volume or radius, the greater the charge density or
polarising power, this in turn leads to more covalent character in the
e.g. chloride and increased acidity of the hexa–aqua–ion [M(H2O)6]n+(aq).
that is with increase in the n+ value.
Note that as the oxidation state
of the transition metal increases,
i.e. increase in charge if an
ionic compound, the greater the polarising power of the cation, which
increases the covalent character of the compound, exemplified by
comparing iron(II) and iron(III) compounds or complex ions
e.g. FeCl2 is
essentially an ionic compound and FeCl3 covalent in
character,
the greater the polarising
power of the central metal ion, the greater the acidity of the hexaaqua
ion
e.g. [Fe(H2O)6]3+
is more acidic than [Fe(H2O)6]2+
Going from iron(II) to iron(III)
involves an increases in cationic positive charge and decrease in radius
of the 'isolated' central metal ion.
The decrease in radius is bound to
result from the same nuclear charge of 26+ 'pulling in' 24 and 23
electrons respectively,
i.e. less electron density in the same quantum
level, less space occupied.
For more details see
Transition Metals Appendix 1 Acidity of
hexaaqua–ions
Relative polarising power of
Groups 1–3 ions for comparison with the 3d block
ions above:
