inorganic chemistry

Module CHEM3101: Lanthanides & Actinides

Lecture 1

(Dr) Jeremy Karl Cockcroft

Department of Chemistry, UCL

[email protected]

[email protected]

CIB: try X-ray rooms 312/313 (305)

3101: Lanthanides & Actinides 2

CHEM3101 Module Synopsis 1. Lanthanides and Actinides

Jeremy Karl Cockcroft (8 lectures) Coursework: Moodle test with Feedback

2. Organometallic Transition Metal Chemistry Claire Carmalt (8 lectures)

Coursework: Traditional

3. Inorganic Spectroscopy Andrew Beale (8 lectures)

Coursework: Moodle test

4. Advanced Inorganic Materials Chemistry: Processes and Applications Jawwad Darr (8 lectures)

Coursework : Moodle test


Timetable

Term Week UCL Week Date 11am 12pm Date 9am 10am

1 5 Mon 22 Sep 2014

2 6 Mon 29 Sep 2014 JKC CJC Wed 01 Oct 2014 JKC CJC

3 7 Mon 06 Oct 2014 Spare CJC Wed 08 Oct 2014 Spare CJC

4 8 Mon 13 Oct 2014 JKC CJC Wed 15 Oct 2014 JKC CJC

5 9 Mon 20 Oct 2014 JKC CJC Wed 22 Oct 2014 JKC CJC

6 10 Mon 27 Oct 2014 JKC Spare Wed 29 Oct 2014 JKC Spare

7 11 Mon 03 Nov 2014

8 12 Mon 10 Nov 2014 JAD JAD Wed 12 Nov 2014 AMB AMB



11 15 Mon 01 Dec 2014 JAD JAD Wed 03 Dec 2014 AMB AMB

12 16 Mon 08 Dec 2014 Spare Spare Wed 10 Dec 2014 Spare Spare

JAD = Jawwad Darr

CJC = Claire Carmalt

Lanthanide & Actinide Chemistry

Inorganic spectroscopy

Room

Course Questionnaire

Roberts 508 Medawar G01 Lankester LT

Reading Week

JKC = Jeremy Karl Cockcroft Materials Chemistry

AMB = Andrew Beale Organometallic Chemistry

CHEM3101 Lecture Timetable (Autumn 2014)

Induction Week


Ln & An Coursework 2014

JKC previously had an in-class test

Replaced by a Moodle Quiz Objectives:

To test current comprehension on material covered

Provide quick assessment scores regarding performance

Improve feedback time on coursework

Version for 2014/15 now has built-in feedback Much improved over version used for 2013/14

Must be taken within a 24 hour period Date yet to be fixed but as soon as possible after end of

lecture series and so as to avoid other coursework deadlines

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Course Overview Introduction

Definition of the f elements & position in periodic table

Lanthanides Discovery of lanthanides

Occurrence & extraction

Properties of the atoms and ions Electronic configurations

Ionisation energies

Metallic and ionic radii

Colour and electronic spectroscopy

Magnetism

Applications of the lanthanides

Coordination chemistry

Organometallic compounds


Course Overview (cont.) Radioactivity

Actinides Discovery of actinides

Abundance & extraction of Th, Pa & U

Synthesis of trans-Uranium elements

Properties of the atoms and ions Electronic configurations Electrode potentials Metallic and ionic radii

Applications of the radioactivity of the actinides

Magnetism

Colour and electronic spectroscopy

Coordination compounds

Organometallic compounds


Aims & Objectives

Define and name the f block elements

Relate history & discovery of lanthanides to their chemistry and abundance

To learn about electronic configuration of lanthanides

To understand preference for certain oxidation states in terms of either ionization energies or electrode potentials

To learn about the lanthanide contraction


Literature

Key textbook: Oxford Chemistry Primer:

The f Elements by Nikolas Kaltsoyannis & Peter Scott, current price 10.99 from Amazon (UK)


Literature

Secondary textbook: : "Lanthanide and Actinide

Chemistry" by Simon Cotton, published by Wiley (but expensive at 35?)


Other Literature

General inorganic chemistry textbooks: Chemistry of the Elements by Greenwood &

Earnshaw, 2nd Edition, Pergamon Press, Chapters 20, 30 and 31

Advanced Inorganic Chemistry by F. A. Cotton, G. Wilkinson, C. A. Murillo & M. Bochmann. 6th Edition, John Wiley & Sons, pp. 1108 1163


Useful Web Sites Web sites for JKC's lectures:

http://moodle.ucl.ac.uk/ Gapped handouts

Powerpoint presentation as used

Periodic Table of the Elements web sites: http://www.webelements.com/

http://www.chemicalelements.com/

http://nautilus.fis.uc.pt/st2.5/

Portugese site but also version in English

Other lecture courses on Ln & An http://www.chem.ox.ac.uk/icl/heyes/LanthAct/lanthac

t.html 3101: Lanthanides & Actinides 12

The f Elements in the News

3101: Lanthanides & Actinides 13 3101: Lanthanides & Actinides 14

See also:

http://www.bbc.co.uk/news/business-18778728


The f Elements Elements with a partially filled f electron

shell including end members with 0 and 14 f electrons

Compare to the d elements (Transition Metals) with 0 to 10 d electrons

Lanthanides Ln (4f) Historically known as the Rare Earths

As oxides

Actinides (5f) Historically known as the Radio(active) Elements

Other radioactive elements


f orbitals In 1918 Bohr realised that the filling of the

electron orbitals around an atom went as follows: n = 1 s2 2e

n = 2 s2 + p6 8e

n = 3 s2 + p6 + d10 18e

n = 4 s2 + p6 + d10 + f 14 32e

n = 5 s2 + p6 + d10 + f 14 (+ g18)

n = 6 s2 + p6 + d10 etc.

Order of filling: Recall 4s > 3d ; likewise 5s, 5d, 5p and 6s > 4f

AnuPen

AnuPen

AnuPen

AnuTypewritten Text

AnuTypewritten TextOn the other hand USA notextracting it's own rareearths - preserving stock...

AnuTypewritten Text


f orbitals l = 3 3 nodal planes in angular function

n 4 (n l 1) nodes in radial function

ml from l to +l (3, 2, 1, 0, 1, 2, 3) 7 f orbitals

s = 14 f electrons and 14 f block elements

What do they actually look like? Visit Mark Winter's web site:

http://winter.group.shef.ac.uk/orbitron/


4f orbitals

No unique

general set as for

s and p orbitals

As for d orbitals,

use a symmetry-

adapted set for

cubic symmetry:

Octahedral

Tetrahedral

Different colours

to show sign of wavefunction


4f orbitals: fx3, fy3, fz3

3 nodal planes in angular function (l = 3) 0 nodes in the radial distribution function (n l 1) 3 functions give lobes that lie along x, y, and z

some similarity with dz2


4f orbitals: fx(z2y2), fy(z2x2), fz(x2y2), fxyz

3 nodal planes in angular function (l = 3) 0 nodes in the radial distribution function (n l 1) 4 functions give lobes that lie between x, y, and z

two interlocking tetrahedra some similarity with dxy

AnuHighlight

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Key Points f orbitals have a relatively large number

of nodal planes in angular function Diffuse orbitals (long, thin lobes)

Sensitive to effective charge on nucleus Implications for filling of the orbitals

Implications for the chemistry of the f elements


The Lanthanides


Lanthanide (Ln) Name Order Lanthanum (La) Cerium(Ce) Praseodymium (Pr)

Neodymium (Nd) Promethium (Pm) Samarium (Sm)

Europium (Eu) Gadolinium (Gd) Terbium (Tb)

Dysprosium (Dy) Holmium (Ho) Erbium (Er)

Thulium (Tm) Ytterbium (Yb) Lutetium (Lu)

Mnemonic:

Late College Parties Never Produce Sexy European

La Ce Pr Nd Pm Sm Eu

Girls/Guys That Drink Heavily Even Though You Look!

Gd Tb Dy Ho Er Tm Yb Lu

Note: key ones to remember regarding position in the periodic table are Ce

(1st with f electrons), Eu (6th), and Gd (7th)


Nomenclature & Discovery Rare Earths are actually oxides: M2O3

Yttrium (Group III) has very similar properties to lanthanides (all of which are rare earths) so is considered as a RE

Many are not actually rare - just difficult to isolate in pure form

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Nomenclature & Discovery Rare earths (RE) were discovered by the Swedish-

Finnish chemist & mineralogist, J. Gadolin as long ago as 1794 at the Ytterby feldspar mine, the latter being a small village near Vaxholm, a small town close to Stockholm, Sweden Mineral named yttria after the place, but later named

gadolinite after its discoverer


Nomenclature & Discovery




3101: Lanthanides & Actinides 29 3101: Lanthanides & Actinides 30


Nomenclature & Discovery In 1803 cerium was discovered by Jns Jacob

Berzelius and Wilhelm Hisinger (Sweden); independently by Martin Klaproth (Germany) Named after the asteroid Ceres which was

discovered 2 years before in 1801


Nomenclature & Discovery In 1839 Carl Gustav Mosander (Sweden)

recognized the element lanthanum in impure cerium nitrate Extraction resulted in the oxide lanthana (La2O3)

From the Greek word lanthanein meaning to lie hidden


Nomenclature & Discovery In 1842 Carl Gustav Mosander (Sweden) separated

"yttria", found in the mineral gadolinite, into three fractions which he called yttria, erbia, and terbia

Names erbia and terbia became confused in this early period: after 1860, Mosander's terbia was known as erbia, and after 1877, the earlier known erbia became terbia.

The erbia of this period was later shown to consist of five oxides, now known as erbia, scandia, holmia, thulia and ytterbia

Erbium, terbium, ytterbium are all named after Ytterby (as is the element yttrium), while holmium is named after the Greek name for Sweden, ie. Holmia (same holm as in Vaxholm, Stockholm, etc., meaning small island)


Nomenclature & Discovery 1853 samarium discovered spectroscopically by its

sharp absorption lines Chemist Jean Charles Galissard de Marignac (Switzerland)

in an earth called didymia

Samarium was chemically isolated in 1879 by Lecoq de Boisbaudran (France) from the mineral "samarskite" (named in honour of a Russian mine official, Colonel Samarski)


Nomenclature & Discovery 1878 Jean Charles Galissard de Marignac also

discovers "ytterbia" in the RE known as "erbia" Later in 1907 Georges Urbain (France) separated ytterbia into two

components, which he called neoytterbia and lutecia: the elements in these earths are now known as ytterbium and lutetium, respectively

Independently discovered by Carl Auer von Welsbach (Germany) and named them cassiopeium and aldebaranium

Lutecium from the Greek word "Lutetia" meaning "Paris"



In 1879 Per Theodor Cleve of Sweden discovered erbium, holmium, thulium while working on the earth "erbia" (from 1843) Latter named after Thule, an ancient

name for Scandinavia


Nomenclature & Discovery In 1880 Jean Charles Galissard de Marignac also

isolated the element gadolinium from Mosander's yttria; independently discovered in 1885 by Lecoq de Boisbaudran who isolated it from Mosander's didymia Gadolinium named after the original discoverer of the rare

earths, J. Gadolin


Nomenclature & Discovery 1885, Carl Auer von Welsbach (Austria) repeatedly

fractionated ammonium didymium nitrate (obtained from samarskite) to get two earths, praseodymia and neodymia, which gave salts of different colours Praseodymium from the Greek prasios didymos meaning

green twin

Neodymium from the Greek neos didymos = new twin


Nomenclature & Discovery 1886 a little dysprosium oxide was identified

by Paul-Emile Lecoq de Boisbaudran (France) as an impurity in erbia Element itself not isolated at that time

Dysprosium from the Greek dysprositos" = hard to obtain


Nomenclature & Discovery The discovery of europium is generally credited to Eugene-

Antole Demarcay who obtained the earth in pure form in 1901 by fractional crystallization of double magnesium nitrates

However, as early as 1892 Lecoq de Boisbaudran had obtained basic fractions from samarium-gadolinium concentrates having spectral lines not accounted for by Sm or Gd; subsequently shown to belong to Eu

Named after "Europe

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen



By the turn of the 20thC 13 out of the 14 f elements had been isolated (plus Y & La)

Why had it taken so long?


Why 100 years to discover? Similarity in the chemistry of the rare-

earths that made them difficult to discover and isolate

No periodic table (and not a huge help anyway) Bohr model of the atom not until 1918

Limited analysis techniques Weighing (assaying from 15thC)

Recrystallization Atomic spectroscopy came about in mid to late 19thC

No instant communication (e.g. Internet) English not the sole language for Science


Nomenclature & Discovery In contrast to other missing elements whose existence were

predicted from the periodic table by Mendeleev, the position of promethium is not so easily predicted by its chemistry In 1945, Marinsky, Glendenin, and Coryell at Oak Ridge, Tennessee,

USA, made the first chemical identification of promethium by use of ion-exchange chromatography on residues in a nuclear reactor

Originally called both Florentium and Illinium but now named after Prometheus in Greek mythology, who stole fire from the gods

Existence predicted by Moseleys Law (1913): = K / (Z )2

X-ray L1 = 2.356 Z = 58 (Ce)

= 2.259 Z = 59 (Pr)

= 2.167 Z = 60 (Nd)

(gap) Z = 61 (???)

= 1.998 Z = 62 (Sm)

= 1.920 Z = 63 (Eu)

= 1.847 Z = 64 (Gd)


Occurence & Abundance Occurence

Most common is Ce (26th in abundance in Earths crust)

Nd is more common than Au

Least common is Tm more common than Iodine Obvious exception is Pm which is radioactive

Two common mineral ores Monazite

Mixed lanthanide/actinide orthophosphate LnPO4 Found in many continents: Asia, South America, Australasia

Bastnaesite Fluorocarbonate LnCO3F

Found mainly in China and in western USA

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Modern Extraction Methods Monazite (several forms)

Crush and grind mineral to a powder

Dissolve in conc. NaOH (70%) at 140C

Add water to precipitate out a mixture of hydroxy/oxide salts Ln(O)(OH) Removes phosphate as soluble sodium salt

Add slurry to boiling HCl acid until pH 3.5 Redissolves 3+ species leaving insoluble ThO2

Add BaCl2 followed by La2(SO4)3 (ratio 3:1) RaSO4 coprecipitated with BaSO4

Solution of mixed rare-earth chlorides


Separation of Rare-Earth Salts

Start with extracted solution from monazite (or bastnaesite) processing

Large scale methods use solvent extraction with complexing agent (nBuO)3PO in inert diluant e.g. kerosene

Separation relies in increasing solubility of Ln3+ with increasing Z

Small scale methods use ion-exchange chromatography (to be discussed later in the course)


Electronic Configuration Periodic Table with Ground States, etc.

http://physics.nist.gov/PhysRefData/PerTable/periodic-table.pdf


Lanthanide Electronic Configuration

Atomic (Neutral Atom) Ground States:

La [Xe]5d1 6s2

Ce [Xe]4f 1 5d 1 6s2 Tb [Xe]4f 9 6s2

Pr [Xe]4f 3 6s2 Dy [Xe]4f 10 6s2

Nd [Xe]4f 4 6s2 Ho [Xe]4f 11 6s2

Pm [Xe]4f 5 6s2 Er [Xe]4f 12 6s2

Sm [Xe]4f 6 6s2 Tm [Xe]4f 13 6s2

Eu [Xe]4f 7 6s2 Yb [Xe]4f 14 6s2

Gd [Xe]4f 7 5d1 6s2 Lu [Xe]4f 14 5d1 6s2

Note those in red (different) & inner (i.e. Xe) versus outer electron shell electrons

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Keypoints re Ln Ground State La and Lu can both be considered as group 3 elements

as they both have a single d electron:

La [Xe]5d1 6s2 Lu [Xe]4f 14 5d1 6s2 Various versions of the periodic table

Lu more like a 3rd row transition metal than La

In the neutral atoms, 5d starts at a lower energy than 4f only for La, Ce, and Gd

Ce [Xe]4f 1 5d1 6s2 Pr [Xe]4f 3 6s2

Stability of -filled shell demonstrated by filling 5d orbital in Gd:

Gd [Xe]4f 7 5d1 6s2 instead of [Xe]4f 8 6s2


Lanthanide Ionization Energies

Ionization energies:

1st Ln (g) Ln+ (g) + e

2nd Ln+ (g) Ln2+ (g) + e

3rd Ln2+ (g) Ln3+ (g) + e

4th Ln3+ (g) Ln4+ (g) + e

Useful to consider sum, e.g.

Ln (g) Ln3+ (g) + 3e

Often quoted in eV Conversion between energy values:

kJ/mole = 96.485309 eV


Ln Lnn+ Ionization Energies


Lanthanide Ionization Energies

Requires more energy to go from Ln3+ (g) to Ln4+ (g) than from Ln (g) to Ln3+ (g)

Chemistry is dominated by 3+ oxidation state

4f orbitals stabilised more than 5d and 6s due to increase in effective charge as a result of ionization of the lanthanide Trivalent (3+) electronic configuration has no 5d or

6s electrons

Other oxidation states result from the stability of empty, -filled, or fully-filled 4f shell


Ln Ln3+ Ionization Energies

4f 76s2 4f 6

4f 146s2 4f 13


Electronic Configuration Ionic Trivalent (3+) Ground States:

La3+ [Xe]

Ce3+ [Xe]4f 1 Tb3+ [Xe]4f 8

Pr3+ [Xe]4f 2 Dy3+ [Xe]4f 9

Nd3+ [Xe]4f 3 Ho3+ [Xe]4f 10

Pm3+ [Xe]4f 4 Er3+ [Xe]4f 11

Sm3+ [Xe]4f 5 Tm3+ [Xe]4f 12

Eu3+ [Xe]4f 6 Yb3+ [Xe]4f 13

Gd3+ [Xe]4f 7 Lu3+ [Xe]4f 14

Again note those in red (sequence followed)


Keypoints re Trivalent State La, Gd, and Lu have empty, -filled, and fully-

filled 4f shell, respectively

Ce3+ and Tb3+ will have empty and -filled 4f shell when ionized to the quadrivalent (4+) oxidation state Expect to find Ce4+ and Tb4+ when stabilised by strong

electronegative ions, e.g. CeO2, TbF4

Ce4+ [Xe] Tb4+ [Xe]4f 7

Eu3+ and Yb3+ will have -filled and fully-filled 4f shell when reduced to the divalent (2+) oxidation state Expect to find Eu2+ and Yb2+ compounds, e.g. EuI2, YbI2


The Elements as Metals Some are kinetically stable in air, but

others oxidize with time...

Photos from web page: http://www.elementsales.com/re_exp/index.htm

Day 0 Day 20 Day 586

AnuPen

AnuPen

AnuPen

AnuPen

AnuPen


Metal Structure & Radii of Ln Element Cryst. Radius() Element Cryst. Radius()

La dhcp 1.879

Ce dhcp 1.832 Tb hcp 1.783

Pr dhcp 1.828 Dy hcp 1.774

Nd dhcp 1.821 Ho hcp 1.766

Pm dhcp 1.811 Er hcp 1.757

Sm rhomb 1.804 Tm hcp 1.746

Eu bcc 2.042 Yb hcp 1.945

Gd hcp 1.801 Lu hcp 1.735 (d)hcp = (double) hexagonal close-packed (ABACA)


Lanthanide Metal Contraction

[Xe]4f 76s2

[Xe]4f 146s2

Contraction arises from the fact that the f electrons provide a poor screen for the valence electrons against the effect of increasing nuclear charge


Ionic Radii of Ln3+

Element Radius() Element Radius()

La 1.061

Ce 1.034 Tb 0.923

Pr 1.013 Dy 0.908

Nd 0.995 Ho 0.894

Pm 0.979 Er 0.881

Sm 0.964 Tm 0.869

Eu 0.950 Yb 0.858

Gd 0.938 Lu 0.848


Lanthanide Cation Contraction

All Ln3+ are [Xe]4f n

Smooth curve for ions in contrast to metal atoms


A Few Consequences of 4f14

Effect on 3rd row transition metals Smaller than might be expected

Radii of Au @ 1.25 versus

Ag @ 1.33

3rd row very similar to 2nd row transition metals in terms of chemical properties

Similar charge density

High density of 3rd row transition metals Os: 22.6 g cm3 compared to

Ru: 12.2 g cm3 or Fe: 7.9 g cm3

and double that of Pb: 11.3 g cm3


Summary Shapes of f orbitals

Diffuse orbitals that are very sensitive to the net effective charge on the nucleus

Similarity in the chemistry of the rare-earths that made them difficult to discover and isolate

Electronic configuration of Ln and Ln3+

Stable oxidation state III

Lanthanide contraction

inorganic chemistry

Documents

lanthanides actinides

jad jad

lectures coursework

actinides magnetism

jkc cjc3

jkc cjc5

jkc cjc6

jkc spare7