# Presentation: 540475

## Chemistry of Selected Lanthanide and Actinide Elements 

- Lester R. Morss
- U.S. Department of Energy
- Office of Basic Energy Sciences

## : Heavy Element Chemistry

**Actinides through Es have been available in macro quantities (********grams or greater); **
**heavier elements have been available only in tracer quantities.**

**:**** Heavy Element Chemistry**

## Long-lived actinide nuclides suitable 

*for physical *
*and chemical investigation*

| Element | Isotope | Half-life |
| --- | --- | --- |
| actinium | 227Ac | 21.772 yr |
| thorium | 232Th | 1.405 x 1010 yr |
| protactinium | 231Pa | 3.276 x 104 yr |
| uranium | 233U | 1.592 x 105 yr |
|  | 238U a | 4.468 x 109 yr |
| neptunium | 237Np | 2.144 x 106 yr |
| plutonium | 238Pu  | 87.7 y |
|  | 239Pu  | 2.411 x 104 y |
|  | 242Pu | 3.733 x 105 yr |
|  | 244Pu | 8.08 x 107 yr |
| americium | 241Am | 432.2 yr |
|  | 243Am | 7370 yr |
| curium | 244Cm | 18.10 yr |
|  | 248Cm | 3.48 x 105 yr |
| berkelium | 247Bk c | 1380 yr |
|  | 249Bk | 330 d |
| californium | 249Cf | 351 yr |
|  | 252Cf | 2.645 yr |
| einsteinium | 253Es | 20.47 d |
|  | 254Es | 275.7 d |
| fermium | 257Fm | 100.5 d |

- aNatural isotopic composition is 99.275% 238U, 0.720% 235U and 0.005% 234 U. Half-life given is for the major constituent 238U**.**
- bProduced only in very small amounts from neutron irradiations in thermonuclear explosions.
- cProduced so far only in tracer quantities from charged particle irradiations.

## Production of transplutonium elements by slow-neutron irradiation

*Nuclear reaction sequence for production of transplutonium elements by intensive slow-neutron irradiation. The principal path is shown by heavy arrows (horizontal, neutron capture; vertical, beta decay). **	**       The sequence above *258*Fm is a prediction.*

## Production of transcurium isotopes in USA a

| 
Isotope | Half-life | Amount/year, 1983 | Amount/campaign, 2004 |
| --- | --- | --- | --- |
| 248Cm | 3.48 x 105 yr | 150 mg b | 100 mg b |
| 249Bk | 330 d | 50 mg | 45 mg |
| 249Cf | 351 yr | c | c |
| 252Cf | 2.645 yr | 500 mg |  400 mg |
| 253Es | 20.47 d | 2 mg a |  1-2 mg d |
| 254Es | 275.7 d | 3 g | 4 g |
| 257Fm | 100.5 d | 1 pg | 1 pg |

- a One or two separation campaigns per year until about 1995;
-     one campaign every 18-24 months from about 1995 to 2003.
- b From  decay of 252Cf.
-  c From  decay of 249Bk.
- d Mixed with 0.06-0.3% 254Es; chemical separation of 253Cf followed by its  decay
-     can yield ~200 g of isotopically pure 253Es.

## Representation of the 

- Representation of the
- angular functions for the
- seven real 5f orbitals in the
- axially quantized representation:

- linear combinations of the
- spherical harmonics with
- common |ml| values.
- The resulting real orbitals can be
- described with Cartesian labels
- in the same way as for
- p and d orbitals.
- They are characterized by a
- distinct |ml| value, giving
- axially quantized orbitals
- of , , , and  symmetry
- with respect to the z axis.

## Electronic configurations of 4f and 5f free atoms 

| Lanthanide series |  |  |  | Actinide series |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Element | Gaseous
 atom | M3+(g) | M3+(aq) | Element | Gaseous
atom | M+(g) | M2+(g) | M3+(g) | M3+(aq) | M4+(g) |
| La | 5d6s2 |  |  | Ac | 6d7s2 | 7s2 | 7s |  |  |  |
| Ce | 4f5d6s2 | 4f | 4f | Th | 6d27s2 | 6d7s2 | 5f6d | 5f |  |  |
| Pr | 4f36s2 | 4f2 | 4f2 | Pa | 5f26d7s2 | 5f27s2 | 5f26d | 5f2 |  | (5f) |
| Nd | 4f46s2 | 4f3 | 4f3 | U | 5f36d7s2 | 5f37s2 |  | 5f3 | 5f3 | 5f2 |
| Pm | 4f56s2 | 4f4 | 4f4 | Np | 5f46d7s2 |  |  | 5f4 | 5f4 | (5f3) |
| Sm | 4f66s2 | 4f5 | 4f5 | Pu | 5f67s2 | 5f67s | 5f6 | 5f5 | 5f5 | (5f4) |
| Eu | 4f76s2 | 4f6 | 4f6 | Am | 5f77s2 | 5f77s | 5f7 | 5f6 | 5f6 | 5f5) |
| Gd | 4f75d6s2 | 4f7 | 4f7 | Cm | 5f76d7s2 | 5f77s2 | 5f8 | 5f7 | 5f7 | (5f6) |
| Tb | 4f96s2 | 4f8 | 4f8 | Bk | 5f97s2 | 5f97s | 5f9 | 5f8 | 5f8 | (5f7) |
| Dy | 4f106s2 | 4f9 | 4f9 | Cf | 5f107s2 | 5f107s | 5f10 | 5f9 | 5f9 | (5f8) |
| Ho | 4f116s2 | 4f10 | 4f10 | Es | 5f117s2 | 5f117s | 5f11 | 5f10 | 5f10 | (5f9) |
| Er | 4f126s2 | 4f11 | 4f11 | Fm | 5f127s2 |  |  | 5f11 | 5f11 | (5f10) |
| Tm | 4f136s2 | 4f12 | 4f12 | Md | 5f137s2 |  |  | 5f12 | 5f12 | (5f11) |
| Yb | 4f146s2 | 4f13 | 4f13 | No | 5f147s2 |  | (5f14) | 5f13 | 5f13 | (5f12) |
| Lu | 4f145d6s2 | 4f14 | 4f14 | Lr | (5f146d7s2
or
5f147s27p) |  |  | 5f14 | 5f14 | (5f13) |

*Electronic configurations of 4f and 5f free atoms *
*free ions, and aqueous ions*

## Electronic configurations of 4f and 5f metals

| Lanthanide series |  |  |  | Actinide series |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Element | Solid metal | Gaseous
 atom | +(g) | Element | Solid metal | Gaseous
atom | M2+(g) | M3+(g) | M3+(aq) | M4+(g) |
| La | 5d6s2 |  |  | Ac | 6d7s2 | 6d7s2 | 7s |  |  |  |
| Ce | 4f5d6s2 | 4f5d6s2 | 4f | Th | 6d27s2 | 6d27s2 | 5f6d | 5f |  |  |
| Pr | 4f25d6s2 | 4f36s2 | 4f2 | Pa |  | 5f26d7s2 | 5f26d | 5f2 |  | (5f) |
| Nd | 4f35d6s2 | 4f46s2 | 4f3 | U |  | 5f36d7s2 |  | 5f3 | 5f3 | 5f2 |
| Pm | 4f45d6s2 | 4f56s2 | 4f4 | Np |  | 5f46d7s2 |  | 5f4 | 5f4 | (5f3) |
| Sm | 4f66s2 | 4f66s2 | 4f5 | Pu |  | 5f67s2 | 5f6 | 5f5 | 5f5 | (5f4) |
| Eu | 4f76s2 | 4f76s2 | 4f6 | Am | 5f66d7s2 | 5f77s2 | 5f7 | 5f6 | 5f6 | 5f5) |
| Gd | 4f75d6s2 | 4f75d6s2 | 4f7 | Cm | 5f76d7s2 | 5f76d7s2 | 5f8 | 5f7 | 5f7 | (5f6) |
| Tb | 4f85d6s2 | 4f96s2 | 4f8 | Bk | 5f86d7s2 | 5f97s2 | 5f9 | 5f8 | 5f8 | (5f7) |
| Dy | 4f95d6s2 | 4f106s2 | 4f9 | Cf | 5f107s2 | 5f107s2 | 5f10 | 5f9 | 5f9 | (5f8) |
| Ho | 4f105d6s2 | 4f116s2 | 4f10 | Es | 5f117s2 | 5f117s2 | 5f11 | 5f10 | 5f10 | (5f9) |
| Er | 4f115d6s2 | 4f126s2 | 4f11 | Fm | 5f127s2 | 5f127s2 |  | 5f11 | 5f11 | (5f10) |
| Tm | 4f125d6s2 | 4f136s2 | 4f12 | Md | 5f137s2 | 5f137s2 |  | 5f12 | 5f12 | (5f11) |
| Yb | 4f146s2 | 4f146s2 | 4f13 | No | 5f147s2 | 5f147s2 | (5f14) | 5f13 | 5f13 | (5f12) |
| Lu | 4f145d6s2 | 4f145d6s2 | 4f14 | Lr | (5f146d7s2
or
5f147s27p) | (5f146d7s2
or
5f147s27p) |  | 5f14 | 5f14 | (5f13) |

*Electronic configurations of 4f and 5f *_***metals***_
*and ions*

- “Trivalent” metals in color

## Fundamental Actinide Science: 5f Electron Chemical Bonding

- Localized f electrons

- Metallic f electrons

- Actinide elements are a scientific frontier with unique opportunities and challenges
- Exciting frontier science from 5f electrons:
- Correlated electrons in -Pu (*Nature*, **2001**, 410, 793)
- Superconductivity in PuCoGa5 (*Nature*, **2002**, 420, 297)
- Actinide chemistry and physics can be interpreted through understanding the properties of _localized_ versus _delocalized_       5f electrons

- Fundamental Actinide Science: 5f Electron Chemical Bonding

**Experimental radii of metals**
**with the same number of valence electrons**

- Eu

- Yb

## Transition metals ( f and d series) showing the crossover from delocalized (bonding) to localized (magnetic moments) f- and d-electron behavior 

*Transition metals ( f and d series) showing the crossover from delocalized (bonding) to localized (magnetic moments) f- and d-electron behavior*

## Actinides at High Pressure and Temperature

- Dotted line: atomic volumes expected if only localized 5f electrons were present.
- Changes in the role of the 5f electrons can be achieved by altering pressure and temperature.
- Pressure increases the itinerant nature (stronger bonds) of the 5f electrons.
- The solid arrows depict the change in atomic volumes under pressure: Both Pa and Am adopt an α-uranium structure.
- The increase in Pu atomic volume (dashed arrow) represents a loss of 5f electron character in the bonding upon heating.

- R. G. Haire, Oak Ridge National Laboratory

## Crystal Structures of 

- Crystal Structures of
- Americium Metal at
- Increasing Pressure
- d.h.c.p. *double hexagonal*
*    **closest packed*
- f.c.c. *face centered cubic (also a*
*    **closest packed structure)*
- d.b.c.m. *double body*
*    **centered monoclinic*
- α-U* orthorhombic uranium *
*    **structure*

## Oxidation states and colors of the actinide ions

| Atomic No.
Element | 89
Ac |  | 90
Th | 91
Pa | 92
U | 93
Np | 94
Pu | 95
Am | 96
Cm | 97
Bk | 98
Cf | 99
Es | 100
Fm | 101
Md | 102
No | 103
Lr |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Oxidation states |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1? |  |  |
|  |  |  | (2) |  |  |  |  | (2) |  |  | (2) | (2) | 2 | 2 | 2 |  |
|  |  | 3 | (3) | (3) | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
|  |  |  | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4? |  |  |  |  |
|  |  |  |  | 5 | 5 | 5 | 5 | 5 | 5? |  | 5? |  |  |  |  |  |
|  |  |  |  |  | 6 | 6 | 6 | 6 | 6? |  |  |  |  |  |  |  |
|  |  |  |  |  |  | 7 | 7 | 7? |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  | 8? |  |  |  |  |  |  |  |  |  |

- Bold type = most stable; (	) = unstable; ? = claimed but not substantiated.

*Oxidation states and colors of the actinide ions*

## The oxidation states of the transactinide elements

| Atomic No.
Element | 104
Rf | 105
Db | 106
Sg | 107
Bh | 108
Hs | 109
Mt | 110
Rg | 111 | 112 |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Oxidation states |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  | -1 ? |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  | 0 ? |  | 0 ? |  |  |  |  |  |  |
|  |  |  |  |  |  | 1 ? |  | 3 ? |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  | 2 ? |  | 2 ?   |  |  |  |  |  |  |
|  | 3 | (3) | (3) | 3 | 3 | 3 ? |  | 5 ? |  |  |  |  |  |  |  |
|  | 4 | 4 | 4 | 4 | 4 |  | 4 ? |  | 4 ? |  |  |  |  |  |  |
|  |  | 5 | 5 | 5 |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  | 6 |  | 6 | 6 ? | 6 ? |  |  |  |  |  |  |  |  |
|  |  |  |  | 7 |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  | 8 |  |  |  |  |  |  |  |  |  |  |

**Bold type = most stable; (****	****) **= **unstable; ? **= **predicted but not experimentally substantiated.**

*The oxidation states of the transactinide elements*

## Ionic radii of lanthanides and actinides (coordination number 6) (Shannon, 1976)

*Ionic radii of lanthanides and actinides (coordination number 6) (Shannon, 1976)*

## Ion types and colors for actinide ions in aqueous solution 

*Ion types and colors for actinide ions in aqueous solution*

- Actinyl ions
- [O=M=O]+ and [O=M=O]2+

## Free energies of formation of actinide aqueous ions

- ∆G° =
- ∆H°-T∆S° =
- -n*F*E°

## Free energies of formation of actinide aqueous ions

- ∆G° =∆H°-T∆S°
- = -n*F*E°

- Most stable
- ion lies
- lowest on
- these plots

*F: *Faraday constant
- Eo: Standard reduction
-        potential

- –

- Most stable
- ion lies
- lowest on
- these plots

## Free energies of formation of actinide aqueous ions

- ∆G° =∆H°-T∆S°
- = -n*F*E°

*F: *Faraday constant
- Eo: Standard reduction
-        potential

- –

- All four ions
- can coexist

## Relationship between Microbiological Activity and Predominant Actinide Oxidation State

## Slide 21

## Elution of tripositive lanthanide 

*Elution of tripositive lanthanide *
*and actinide ions *
*on Dowex 50 *
*cation-exchange* *resin *
*and ammonium *
***-hydroxyisobutyrate eluant. *
*Lr*3+ *band (dashed line) was predicted.*

## Enthalpies of

- _Sublimation_ of
- Lanthanide and
- Actinide Metals
- M(s)M(g)

- _Formation_ of
- Lanthanide and
- Actinide Aquo Ions
- M(s) + 3H+(aq)
-     M3+(aq) + 3/2H2

## Enthalpies of

- f6

- f7s2

- f6ds2

- f7ds2

- f7ds2

- _Sublimation_ of
- Lanthanide and
- Actinide Metals
- M(s)M(g)

- _Formation_ of
- Lanthanide and
- Actinide
- Aquo Ions
- M(s) + 3H+(aq)
-  M3+(aq) + 3/2H2
- Eu metal:
-    _di_valent
- Gd metal:
-    _tri_valent

- Eu(s)*

- Gd(s)

- Eu(g)*

- Eu3+(aq)

- Eu(s)

- Gd(g)

- Eu(g)

- Eu(s)*

- Gd3+(aq)

- Gd(s)

- Eu(s)

- f7s2

- f7s2

*Energy*

- f7ds2

- f7

*Energy*

- f6ds2

- Eu metal:
- _di_valent

- Gd metal:
-    _tri_valent

## Relative energies of the 5fN7s2 and 5fN-16d7s2 electron configurations in the gaseous actinide atoms showing the stabilization of the 5fN7s2 as the atomic number Z (Z = 88 + N) increases. 

*Relative energies of the 5f**N**7s**2** and 5f**N-1**6d7s**2** electron configurations in the **gaseous actinide atoms** showing the stabilization of the 5f**N**7s**2** as the atomic number Z (Z = 88 + N) increases.*

*N*

*6d7s**2* *configuration*
*(“trivalent” state)*
*is more stable*

*7s**2* *configuration*
*(“divalent” state)*
*is more stable*

## Enthalpies of

- Solution of
- Actinide
- Sesquioxides
- and Trichlorides
- as Function of
- Cation Size

## Enthalpies of

- Solution of
- Lanthanide
- Sesquioxides
- and Trichlorides
- as Function of
- Cation Size

## Phase Diagram of

- Lanthanide and
- Actinide Sesquioxides as
- Function of Ion Size

## Slide 29

## Relations Among

- Ionization Energies (Upot),
- Enthalpies of Hydration
- (∆Hhyd), and
- Enthalpies of Solution
- (∆Hsoln) of
- Trichlorides and
- Sesquioxides

## Enthalpies of

- Solution of
- Lanthanide
- and Actinide
- Sesquioxides
- and Trichlorides
- as Function of
- Cation Size

## Quartz fiber microbalance
B. B. Cunningham, Univ of Chicago, 1942

- B. B. Cunningham, Univ of Chicago, 1942

- Used to determine mass of a 239PuO2
- sample (2.77 μg) that enabled the
- determination of half-life of 239Pu

- telescope

## Torsion quartz fiber

- Torsion wheel

- Balance beam

- Sample hook

## Slide 34

## Slide 35

## Titrant (C): Fe2+(aqueous)

- Titrant (C): Fe2+(aqueous)
- Titrand (M): Bk4+ from
-  Cs2BkCl6
- Redox reaction:
- Fe2+ + Bk4+ = Fe3+ + Bk3+

## Structure of Cs2BkCl6

- Structure of Cs2BkCl6
- (Unit cell projected on *c* axis)

## Solution-Titration

- Calorimeter

## Slide 39

## Slide 40

## DOE Basic Energy Sciences and National Science Foundation Scientific User Facilities

**Advanced Light Source**

**Stanford Synchrotron Radiation Lab**

**National Synchrotron Light Source**

**Advanced Photon Source**

**Center for Microanalysis of Materials**

**High-Flux Isotope Reactor**

**Intense Pulsed Neutron Source**

**Pulse Radiolysis Facility**

**Los Alamos Neutron Science Center**

**Center for Nanophase Materials Sciences**

**Spallation Neutron Source**

**Linac Coherent Light Source**

**Center for Integrated Nanotechnologies**

**Molecular**
**Foundry **

**Center for Nanoscale Materials**

**DOE Basic Energy Sciences and National Science Foundation Scientific User Facilities**

**Center for Functional Nanomaterials**

**Environmental Molecular Science Institute**

**Environmental Molecular Science Institute**

## Opportunities for Actinide Chemistry Speciation and Characterization to Advance Environmental Science

**U.S. Contaminated Sites**

**Russian Contaminated Sites**

**Fundamental understanding of actinide behavior under a broad range of conditions can help countries with environmental issues**
**Advanced speciation techniques**
**Structural chemistry**
**Assessing the role of colloids & humic acids**
**Interfacial science of actinides**
**Development of scientifically-based models**
**Predictive capability**
**Science-based remediation**