Geology Reference
In-Depth Information
the same wavelength leading to reinforcement (if
'in-phase') or attenuation (if 'out of phase'). See
Figure 5.3.1(b) and (c).
Interstitial
Situated in cavities between larger atoms
or ions in a regular crystal structure.
Invariant
Describes a point in a phase diagram that
has zero variance
F
(see discussion of Figure 2.1).
Inversion
Recrystallization of a crystalline phase to a
more stable polymorph.
Ion
Atom with a net electrical charge, due to the acqui-
sition or loss of
electron
(s). See
anion
and
cation.
Ion pair
Temporary electrostatic association in solu-
tion of two ions of opposite charge.
Ionic potential
Ratio of an ion's nominal charge over
its ionic radius.
Ionic strength
Isotropic
Describes a substance whose physical
properties have values that are independent of the
direction in which they are measured.
Kelvin, K
Unit of temperature expressed on the
absolute temperature scale.
T
/K =
T
/˚C + 273.15.
The kelvin (K) and degree Celsius (˚C) have the
same magnitude but differ in their zero points
(absolute zero and the melting point of ice
respectively).
Kilobar (kbar, kb)
1 kb = 10
8
Pa. See
bar
.
Kiloelectron-volt (keV)
1000 electron-volts.
Kinetic energy (
E
k
)
The energy a body possesses by
virtue of its motion. See Chapter 1.
I
=
∑
2
1
2
mz
, a measure of how far an
Lanthanide
One of the 14 elements following lantha-
num in the Periodic Table, characterized by the entry
of
electrons
into the 4f orbitals.
Latent heat of fusion
The enthalpy required to trans-
form 1 kg of a solid completely into a liquid at constant
temperature (J kg
−1
)
Latent heat of vaporization
The enthalpy required
to transform 1 kg of a liquid into a gas at constant
temperature (J kg
−1
)
Ligand
(in a co-ordination
complex
or crystal) The
ions or molecules surrounding the central ion
or atom. For example in the dissolved complex
Cu(HS)
2
−
, the ligands are the two HS
−
anions attached
to the central Cu
+
ion.
Linear
A relationship between
y
and
x
is said to be
linear if plotting
y
against
x
yields a straight line.
Liquidus
The temperature at which the first crystals
begin to form in a cooling melt. A liquidus curve (or
surface) shows the variation of liquidus temperature
with composition or with pressure.
Logarithm (log, ln)
The magnitude of a number
expressed as a power of 10 (log
10
) or of
e
(natural
logarithm = ln), as explained in Appendix A.
Lone pair
Paired valence electrons in a filled lobe of
(usually) a hybrid orbital (e.g. Figure 7.5b, c). Lone
pairs influence hybrid shape, and are involved as
electron donors in the formation of co-ordination
complexes
.
ii
i
ionic solution departs from
ideal solution
behav-
iour.
I
= ionic strength,
m
i
= molality of ion species
i
,
z
i
= charge on ion species
i
. See Appendix D for
explanation of Σ.
Ionization energy
The energy (in eV or kJ mol
−1
)
required to remove the most easily detached
electron
from an atom to a state of rest at infinity (Figure 5.6).
Ionization potential
Obsolete synonym for
ioniza-
tion energy
.
Iso-
Prefix meaning 'having the same …' .
Isobar, isobaric
(a) A pressure 'contour', a hypotheti-
cal line or surface in
P-T-X
space at which pressure
is everywhere uniform. 'Isobaric' signifies a process
that occurs at constant pressure. (b)
Nuclide
having
the same mass number
A
(Box 6.1) as another.
Isochron
A line on an isotope-ratio plot drawn
through data points having the same age.
Isotherm, isothermal
A temperature contour in a
phase diagram. A line or surface on which tempera-
ture is constant. 'Isothermal' signifies a process
operating (or a phase diagram constructed) at con-
stant temperature.
Isotone
See Box 10.1.
Isotope
An isotope of an element consists of nuclei
that share the same values of
atomic number
Z
and
neutron number
N
. Other isotopes of the element
have the same value of
Z
but different value(s) of
N
.
See Box 10.1.
Isotopic tracer
An isotopic ratio differing between
one type of source material and another, that indi-
cates the derivation of a rock or solution.
Macroscopic
Visible to the naked eye or measurable
with normal laboratory apparatus, as opposed to
microscopic.
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