Lecture 2 (9/11/2006) –
Crystal Chemistry
Part 1:
Atoms, Elements, and Ions
Mineralogy Website
www.d.umn.edu/~mille066/Teaching/Mineralogy06.htm
What is Crystal Chemistry?
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study of the atomic structure, physical properties,
and chemical composition of crystalline material
basically inorganic chemistry of solids
the structure and chemical properties of the atom
and elements are at the core of crystal chemistry
there are only a handful of elements that make
up most of the rock-forming minerals of the earth
Chemical Layers of the Earth
SiO2 – 45%
MgO – 37%
FeO – 8%
Al2O3 – 4%
CaO – 3%
others – 3%
Fe – 86%
S – 10%
Ni – 4%
Composition of the Earth’s Crust
Average composition of the Earth’s Crust
(by weight, elements, and volume)
The Atom
The Bohr Model
Nucleus
The Schrodinger Model
- contains most of the weight (mass) of the atom
- composed of positively charge particles (protons) and neutrally
charged particles (neutrons)
Electron Shell
- insignificant mass
- occupies space around the nucleus defining atomic radius
- controls chemical bonding behavior of atoms
Elements and Isotopes
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Elements are defined by the number of protons in the
nucleus (atomic number).
In a stable element (non-ionized), the number of electrons
is equal to the number of protons
Isotopes of a particular element are defined by the total
number of neutrons in addition to the number of protons
in the nucleus (isotopic number).
Various elements can have multiple (2-38) stable isotopes,
some of which are unstable (radioactive)
Isotopes of a particular element have the same chemical
properties, but different masses.
Isotopes of Titanium (Z=22)
Isotope
38Ti
39Ti
40Ti
41Ti
42Ti
43Ti
44Ti
45Ti
46Ti
47Ti
48Ti
49Ti
50Ti
51Ti
52Ti
53Ti
54Ti
55Ti
56Ti
57Ti
58Ti
59Ti
60Ti
61Ti
Half-life
0+
26 ms
50 ms
80 ms
199 ms
509 ms
63 y
184.8 m
stable
stable
stable
stable
stable
5.76 m
1.7 m
32.7 s
320 ms
160 ms
180 ms
Spin Parity
Decay Mode(s) or Abundance
(3/2+)
0+
3/2+
0+
7/20+
7/20+
5/20+
7/20+
3/20+
(3/2)0+
(3/2-)
0+
(5/2-)
0+
(5/2-)
0+
(1/2-)
EC=100, ECP+EC2P ~ 14
EC+B+=100
EC+B+=100, ECP ~ 100
EC+B+=100
EC+B+=100
EC=100
EC+B+=100
Abundance=8.0 1
Abundance=7.3 1
Abundance=73.8 1
Abundance=5.5 1
Abundance=5.4 1
B-=100
B-=100
B-=100
B-=100
B-=100, B-N=0.06 sys
B-=100, B-N=0.04 sys
B-=?
B-=?
B-=?, B-N=?
Source: R.B. Firestone
UC-Berkeley
Properties of Electrons
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Occur in discrete (quantized) energy levels or orbitals
around the nucleus
Behave as particles with wave-like properties
Position of an electron in space around the nucleus is a
probability function defined by 4 quantum numbers
n – principle quantum number (= 1, 2, 3, 4...)
defines the energy level of the primary electron shell
l – azimuthal quantum number (= n -1)
defines the type and number of electron subshells (s, p, d, f, ...)
m – magnetic quantum number (= +l to -l )
defines orientation and number of orbitals in each subshell
s – spin quantum number (= +1/2 or -1/2)
defines direction of spin of the electron in each orbital
Electron Shells, Subshells, and Orbitals
Filling up the
Orbitals
Controlled by the energy
of the orbitals
Structure of the Periodic Table
# of Electrons in Outermost Shell
Noble
Gases
Anions
--------------------Transition Metals------------------
Primary Shell being filled
Ions, Ionization Potential, and Valence States
Cations – elements prone to give up one or more electrons
from their outer shells; typically a metal element
Anions – elements prone to accept one or more electrons
to their outer shells; always a non-metal element
Ionization Potential – measure of the energy necessary to
strip an element of its outermost electron
Electronegativity – measure strength with which a nucleus
attracts electrons to its outer shell
Valence State (or oxidation state) – the common ionic
configuration(s) of a particular element determined by
how many electrons are typically stripped or added to an
ion
1st Ionization Potential
Anions
Cations
Elements with a single
outer s orbital electron
Electronegativity
Valence States of Ions common to
Rock-forming Minerals
+1 +2
+3 +4 +5 +6 +7
-2 -1
-----------------Transition Metals---------------
Cations – generally
relates to column
in the periodic
table; most
transition metals
have a +2
valence state for
transition metals,
relates to having
two electrons in
outer
Anions – relates
electrons needed
to completely fill
outer shell
Anionic Groups –
tightly bound
ionic complexes
with net negative
charge
Next Lecture
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Crystal Chemistry II
Bonding
Atomic and Ionic Radii
Read p. 56-69