Lecture 2 (9/11/2006) – Lecture 2 (9/11/2006) –

Crystal ChemistryCrystal Chemistry

Part 1: Part 1:

Atoms, Elements, and Atoms, Elements, and IonsIons

Mineralogy WebsiteMineralogy Website

www.d.umn.edu/~mille066/Teaching/www.d.umn.edu/~mille066/Teaching/Mineralogy06.htmMineralogy06.htm

What is Crystal Chemistry?What is Crystal Chemistry?

study of the atomic structure, physical study of the atomic structure, physical properties, and chemical composition of properties, and chemical composition of crystalline material crystalline material

basically inorganic chemistry of solidsbasically inorganic chemistry of solids the structure and chemical properties of the the structure and chemical properties of the

atom and elements are at the core of crystal atom and elements are at the core of crystal chemistry chemistry

there are only a handful of elements that there are only a handful of elements that make up most of the rock-forming minerals make up most of the rock-forming minerals of the earthof the earth

Fe – 86%Fe – 86%S – 10%S – 10%Ni – 4%Ni – 4%

Chemical Layers of the EarthChemical Layers of the Earth

SiO2 – 45%SiO2 – 45%MgO – 37%MgO – 37%FeO – 8%FeO – 8%Al2O3 – 4%Al2O3 – 4%CaO – 3% CaO – 3% others – 3%others – 3%

Composition of the Earth’s CrustComposition of the Earth’s Crust

Average composition of the Earth’s Average composition of the Earth’s CrustCrust

(by weight, elements, and volume)(by weight, elements, and volume)

The AtomThe Atom

The Bohr Model The Schrodinger ModelNucleus

- 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 IsotopesElements and Isotopes

Elements are defined by the number of protons in Elements are defined by the number of protons in the nucleus (atomic number). the nucleus (atomic number).

In a stable element (non-ionized), the number of In a stable element (non-ionized), the number of electrons is equal to the number of protonselectrons is equal to the number of protons

Isotopes of a particular element are defined by the Isotopes of a particular element are defined by the total number of neutrons in addition to the number total number of neutrons in addition to the number of protons in the nucleus (isotopic number). of protons in the nucleus (isotopic number).

Various elements can have multiple (2-38) stable Various elements can have multiple (2-38) stable isotopes, some of which are unstable (radioactive)isotopes, some of which are unstable (radioactive)

Isotopes of a particular element have the same Isotopes of a particular element have the same chemical properties, but different masses. chemical properties, but different masses.

Isotopes of Titanium (Z=22)Isotope Half-life Spin Parity Decay Mode(s) or Abundance38Ti 0+ 39Ti 26 ms (3/2+) EC=100, ECP+EC2P ~ 14 40Ti 50 ms 0+ EC+B+=100 41Ti 80 ms 3/2+ EC+B+=100, ECP ~ 100 42Ti 199 ms 0+ EC+B+=100 43Ti 509 ms 7/2- EC+B+=100 44Ti 63 y 0+ EC=100 45Ti 184.8 m 7/2- EC+B+=100 46Ti stable 0+ Abundance=8.0 1 47Ti stable 5/2- Abundance=7.3 1 48Ti stable 0+ Abundance=73.8 1 49Ti stable 7/2- Abundance=5.5 1 50Ti stable 0+ Abundance=5.4 1 51Ti 5.76 m 3/2- B-=100 52Ti 1.7 m 0+ B-=100 53Ti 32.7 s (3/2)- B-=100 54Ti 0+ 55Ti 320 ms (3/2-) B-=100 56Ti 160 ms 0+ B-=100, B-N=0.06 sys 57Ti 180 ms (5/2-) B-=100, B-N=0.04 sys 58Ti 0+ 59Ti (5/2-) B-=? 60Ti 0+ B-=? 61Ti (1/2-) B-=?, B-N=? Source: R.B. Firestone

UC-Berkeley

Properties of ElectronsProperties of Electrons

Occur in discrete (quantized) energy levels or Occur in discrete (quantized) energy levels or orbitals around the nucleusorbitals around the nucleus

Behave as particles with wave-like propertiesBehave as particles with wave-like properties Position of an electron in space around the nucleus is Position of an electron in space around the nucleus is

a probability function defined by 4 quantum numbersa probability function defined by 4 quantum numbersnn – principle quantum number (= 1, 2, 3, 4...) – principle quantum number (= 1, 2, 3, 4...)

defines the energy level of the primary electron shelldefines the energy level of the primary electron shellll – azimuthal quantum number (= – azimuthal quantum number (= n n -1)-1)

defines the type and number of electron subshells (s, p, defines the type and number of electron subshells (s, p, d, f, ...)d, f, ...)mm – magnetic quantum number (= + – magnetic quantum number (= +ll to - to -l l ))

defines orientation and number of orbitals in each defines orientation and number of orbitals in each subshellsubshellss – spin quantum number (= +1/2 or -1/2) – spin quantum number (= +1/2 or -1/2)

defines direction of spin of the electron in each orbitaldefines direction of spin of the electron in each orbital

Electron Shells, Subshells, and Electron Shells, Subshells, and OrbitalsOrbitals

Filling up the Filling up the OrbitalsOrbitals

Controlled by the energy of the orbitals

Structure of the Periodic TableStructure of the Periodic Table# of Electrons in Outermost Shell Noble

Gases

Anions

--------------------Transition Metals------------------

Primary Shell being filled

Ions, Ionization Potential, and Valence Ions, Ionization Potential, and Valence StatesStates

CationsCations – elements prone to give up one or more electrons from – elements prone to give up one or more electrons from their outer shells; typically a metal elementtheir outer shells; typically a metal element

AnionsAnions – elements prone to accept one or more electrons to – elements prone to accept one or more electrons to their outer shells; always a non-metal elementtheir outer shells; always a non-metal element

Ionization PotentialIonization Potential – measure of the energy necessary to strip – measure of the energy necessary to strip an element of its outermost electron an element of its outermost electron

ElectronegativityElectronegativity – measure strength with which a nucleus – measure strength with which a nucleus attracts electrons to its outer shellattracts electrons to its outer shell

Valence StateValence State (or oxidation state) – the common ionic (or oxidation state) – the common ionic configuration(s) of a particular element determined by how configuration(s) of a particular element determined by how many electrons are typically stripped or added to an ionmany electrons are typically stripped or added to an ion

1st Ionization Potential

Electronegativity

Elements with a single outer s orbital electron

Anions

Cations

Valence States of Ions common Valence States of Ions common to Rock-forming Mineralsto Rock-forming Minerals

CationsCations – generally – generally relates to column relates to column in the periodic in the periodic table; most table; most transition metalstransition metals have a +2 have a +2 valence state for valence state for transition metals, transition metals, relates to having relates to having two electrons in two electrons in outer outer

AnionsAnions – relates – relates electrons needed electrons needed to completely fill to completely fill outer shellouter shell

Anionic Groups – Anionic Groups – tightly bound tightly bound ionic complexes ionic complexes with net negative with net negative chargecharge

+1 +2 +3 +4 +5 +6 +7

-2 -1

-----------------Transition Metals---------------

Next LectureNext Lecture

Crystal Chemistry IICrystal Chemistry II

BondingBonding

Atomic and Ionic RadiiAtomic and Ionic Radii

Read p. 56-69 Read p. 56-69