fermium ← mendelevium → nobelium Tm ↑ Md ↓ (Upu) 101Md Periodic table
Appearance
unknown
General properties
Name, symbol, number	mendelevium, Md, 101
Pronunciation	/ˌmɛndəˈlɛviəm/ or /ˌmɛndəˈliːviəm/
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(258)
Electron configuration	[Rn] 5f13 7s2
Electrons per shell	2, 8, 18, 32, 31, 8, 2 (Image)
Physical properties
Phase	solid
Melting point	1100 K, 827 °C, 1521 °F
Atomic properties
Oxidation states	2, 3
Electronegativity	1.3 (Pauling scale)
Ionization energies	1st: 635 kJ·mol−1
Miscellanea
Magnetic ordering	no data
CAS registry number	7440-11-1
Most stable isotopes
Main article: Isotopes of mendelevium
iso NA half-life DM DE (MeV) DP 257Md syn 5.52 h ε 0.406 257Fm α 7.558 253Es SF - - 258Md syn 51.5 d ε 1.230 258Fm 260Md syn 31.8 d SF - - α 7.000 256Es ε - 260Fm β− 1.000 260No
v t e · r

Mendelevium ( /ˌmɛndəˈlɛviəm/ or /ˌmɛndəˈliːviəm/) is a synthetic element with the symbol Md (formerly Mv) and the atomic number 101. A metallic radioactive transuranic element in the actinide series, mendelevium is usually synthesized by bombarding einsteinium with alpha particles. It was named after Dmitri Ivanovich Mendeleev, who created the Periodic Table. Mendeleev's periodic system is the fundamental way to classify all the chemical elements. The name "mendelevium" was accepted by the International Union of Pure and Applied Chemistry (IUPAC). On the other hand, the proposed symbol "Mv" submitted by the discoverers was not accepted, and IUPAC changed the symbol to "Md" in 1963.^[1]

Characteristics[link]

Researchers have shown that mendelevium has a moderately stable dipositive (II) oxidation state in addition to the more characteristic (for actinide elements) tripositive (III) oxidation state, the latter being the more dominantly exhibited state in an aqueous solution (chromatography being the process used). Sometimes, mendelevium can even be shown to exhibit a monopositive (I) state. ²⁵⁶Md has been used to find out some of the chemical properties of this element while in an aqueous solution. There are no other known uses of mendelevium and only trace amounts of the element have ever been produced. Other isotopes of mendelevium, all radioactive, have been discovered, with ²⁵⁸Md being the most stable with a two-month half-life (about 55 days). Other isotopes range from 248 to 258 mass numbers and half-lives from a few seconds to about 51 days. The original ²⁵⁶Md had a half-life of 87 minutes.

Radioactivity[link]

The trivalent element is radioactive. It was expected that the reaction would be²⁵³Es (α,n) ²⁵⁵Md, where ²⁵⁵Md was α-active with a t_½ of 5 minutes and the corresponding α-energy. No such α-activity was observed, but the 101 fraction showed spontaneous fission representing a t_½ less than 3 hours. Because spontaneous fission was also observed in the fraction containing fermium, the α-bombardment of ²⁵³Es produced ²⁵⁶Md. The latter underwent electron capture to become ²⁵⁶Fm, which then decayed by spontaneous fission. So ²⁵⁶Fm was produced by the decays of cyclotron-synthesized mendelevium.^[2]

Metallic state[link]

Johansson and Rosengren predicted in 1975 that Md would prefer a divalent metallic state, similar to europium (Eu) and ytterbium (Yb), rather than a trivalent one. Thermochromatographic studies conducted with trace amounts of Md concluded that Md forms a divalent metal. With the aid of empirical correlation method, a divalent metallic radius of (0.194 ± 0.010) nm has been estimated. The estimated enthalpy of sublimation is in the range of 134-142 kJ/mol.^[3]

Solution chemistry[link]

Before the actual discovery of mendelevium, the trivalent state was the most stable one in aqueous solution. Accordingly, a similar chemical behavior to the other 3+ actinides and lanthanides was expected. The elution of Md just before Fm in the elution sequence of the trivalent actinides from the cation-exchange resin column, confirmed this prediction. Afterwards, Md in the form of insoluble hydroxides and fluorides that are quantitatively coprecipitated with trivalent lanthanides was found. The cation-exchange resin column as well as the HDEHP solvent extraction column elution date is consistent with a trivalent state for Md and an ionic radius smaller than Fm. An ionic radius of 0.0192 nm and a coordination number of 6 for Md³⁺ was predicted using empirical correlations. Using the known ionic radii for the trivalent rare earths and the linear correlation of log distribution coefficient with ionic radius, an average ionic radius of 0.089 nm was estimated for Md³⁺ and a heat of hydration of – (3654 ± 12) kJ/mol calculated using empirical models and the Born-Haber cycle. In reducing conditions, an anomalous chemical behavior of Md was found. Coprecipitation with BaSO₄ and solvent extraction chromatography experiments using HDEHP were carried out in different reducing agents. These showed that Md³⁺ could easily be reduced to a stable Md²⁺ in aqueous solution. Mendelevium can also be reduced to the monovalent state in water-ethanol solutions. The cocrystallization of Md⁺ with salts of divalent ions is due to the formation of mixed crystals. For Md⁺, an ionic radius of 0.117 nm was found. The oxidation of Md³⁺ to Md⁴⁺ was rather unsuccessful.^[2]

History[link]

Mendelevium (for Dimitri Ivanovich Mendeleev, surname commonly transliterated into Latin script as Mendeleev, Mendeleyev, Mendeléef, or even Mendelejeff, and first name sometimes transliterated as Dmitry or Dmitriy) was first synthesized by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey, and Stanley G. Thompson (team leader) in early 1955 at the University of California, Berkeley. The team produced ²⁵⁶Md (half-life of 87 minutes) when they bombarded an ²⁵³Es target with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory's 60-inch cyclotron (²⁵⁶Md was the first isotope of any element to be synthesized one atom at a time).^[4] Element 101 was the ninth transuranic element synthesized. The first 17 atoms of this element were created and analyzed using the ion-exchange adsorption-elution method. During the process, mendelevium behaved very much like thulium, its naturally occurring homologue.

Discovery in detail[link]

The discovery was based on a grand total of only 17 atoms. It is synthesized via the ²⁵³Es (α,n) ²⁵⁶101 reaction in the 60-Inch-Cyclotron (= 152 cm) at Berkeley (California). The target can be produced by irradiation of lighter isotopes as plutonium in the Materials Testing Reactor at the Arco Reactor Station in Idaho. Remarkable is that this target consisted of only 10⁹ atoms of highly radioactive ²⁵³Es (with a half-life of 20.5 days). By elution through a calibrated cation exchange resin column, mendelevium was separated and chemically identified.^[4]

Determining feasibility[link]

To predict if this method would be possible, they made use of a rough calculation. The number of atoms that would be produced, would be approximately equal to the number of atoms of target material times its cross section times the ion beam intensity times the time of bombardment related to the half-life of the product when bombarding for a time of the order of its half-life). This gave 1 atom per experiment. Thus under optimum conditions, the preparation of only one atom of element 101 per experiment could be expected. This calculation demonstrated that it was feasible to go ahead with the experiment.^[4]

Recoil technique[link]

The actual synthesis was done by a recoil technique, introduced by Albert Ghiorso. In this technique, the target element was placed on the opposite side of the target from the beam and caught the recoiling atoms on a catcher foil. This recoil target was made by an electroplating technique, developed by Alfred Chetham-Strode. This technique gave a very high yield, which is absolutely necessary when working with such a rare product as the einsteinium target material.^[4]

The recoil target consisted of 10⁻⁹ of ²⁵³Es which were deposited electrolytically on a thin gold foil (also Be, Al and Pt can be used). It was bombarded by 41 eV α-particles in the Berkeley cyclotron with a very high beam density of 6∙10¹³ particles per second over an area of 0.05 cm². The target was cooled by water or liquid helium. The use of helium, in a gaseous atmosphere, slowed down the recoil atoms. This gas could be pumped out of the reaction chamber through a small orifice to form a ‘gas-jet’. Some fraction of the nonvolatile product atoms carried along with the gas, were deposited permanently on the foil surface. The foil could be removed periodically and a new foil could be installed. The next reaction was used for the mendelevium discovery experiment:^{[4][5] 253}Es + ⁴He → ²⁵⁶Md + ¹n.

Purification and isolation[link]

The removal of the Md atoms from the collector foil was done by acid etching or total dissolution of the thin gold foil. They can be purified and isolated from other product activities by several techniques. Separation of trivalent actinides from lanthanide fission products and La carrier can be done by a cation-exchange resin column using a 90% water/10% ethanol solution saturated with HCl as eluant. To separate Md rapidly from the catcher foil, an anion-exchange chromatography using 6M HCl as eluant can be used. The gold remained on the column while the Md and other actinides passed through. A final isolation of Md³⁺ from other trivalent actinides was also required. To separate fractions containing elements 99, 100 and 101, a cation-exchange resin column (Dowex-50 exchange column) treated with ammonium salts was used. A chemical identification was made on the basis of its elution position just before Fm. In series of repetitive experiments, they made use of the eluant: α-hydroxyisobutyrate solution (α-HIB). Using the ‘gas-jet’ method, the first two steps can be eliminated. There was shown that in this method it is possible to transport and collect individual product atoms in a fraction of a second some tens of meters away from the target area. Effective transport over long distances requires the presence of large clusters (KCl aerosols) in the ‘carrier’ gas. It is used frequently in the production and isolation of transeinsteinium elements.^[2]

Another possible way to separate the 3+ actinides can be achieved by solvent extraction chromatography using bis-(2-ethylhexyl) phosphoric acid (abbreviated as HDEHP) as the stationary organic phase and HNO₃ as the mobile aqueous phase. The actinide elution sequence is reversed from that of the cation-exchange resin column. The Md separated by this method has the advantage to be free of organic complexing agent compared to the resin column. The disadvantage of this method is that Md elutes after Fm late in the sequence.^[2]

The first "Hooray!"[link]

There was no direct detection, but by observation of spontaneous fission events arising from its electron-capture daughter ²⁵⁶Fm. These events were recorded during the night of February 19, 1955. The first one was identified with a "hooray" followed by a "double hooray" and a "triple hooray". The fourth one eventually officially proved the chemical identification of the 101st element, mendelevium. Additional analysis and further experimentation, showed the isotope to have mass 256 and to decay by electron capture with a half-life of 1.5 h.

Isotopes[link]

Sixteen isotopes of mendelevium from mass 245 to 260 have been characterized, with the most stable being ²⁵⁸Md with a half-life of 51.5 days, ²⁶⁰Md with a half-life of 31.8 days, and ²⁵⁷Md with a half-life of 5.52 hours. All of the remaining radioactive isotopes have half-lives that are less than 97 minutes, and the majority of these have half-lives that are less than 5 minutes. This element also has 5 meta states, with the longest-lived being ^258mMd (t_½ = 58 minutes). The isotopes of mendelevium range in atomic weight from 245.091 u (²⁴⁵Md) to 260.104 u (²⁶⁰Md).^[6][7]

References[link]

Further reading[link]

• Hoffman, D.C., Ghiorso, A., Seaborg, G. T. The transuranium people: the inside story, (2000), 201-229
• Morss, L. R., Edelstein, N. M., Fuger, J., The chemistry of the actinide and transactinide element, 3, (2006), 1630–1636
• Seaborg, G. T., Les elements tranuraniens artificiels, (1967), 39-45
• Gol’danskii, V. I., Polikanov, S. M., The transuranium elements, (1973), 101-103
• Seaborg, G.T., The transcalifornium elements. Journal of Chemical Education, (1959), 36, 38-44
• Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1

External links[link]

Wikimedia Commons has media related to: Mendelevium

Look up mendelevium in Wiktionary, the free dictionary.

• Los Alamos National Laboratory - Mendelevium
• It's Elemental - Mendelevium
• WebElements.com - Mendelevium
• Environmental Chemistry- Md info

vep:Mendelevii

Rich Hall
Hall performing at the Tower Theatre in Upper Darby, Pennsylvania in 1986
Birth name	Richard Hall
Born	(1954-06-10) 10 June 1954 (age 58) Alexandria, Virginia, United States
Medium	Stand-up, television
Nationality	American
Years active	1979—present
Genres	Observational comedy, Deadpan, Political satire
Subject(s)	American culture, British culture, United States politics, British politics
Spouse	Karen Hall
Notable works and roles	QI, Saturday Night Live, Fridays, Late Show with David Letterman
Website	http://www.offthekerb.co.uk/rich-hall/

Richard "Rich" Hall (born 10 June 1954) is an American comedian, writer and musician.

Early life and career[link]

Hall was born in Alexandria, Virginia and grew up in Mecklenburg County, North Carolina. He is part Cherokee Indian and his mother's Christian name is Doris.^[1] Early in his career, he performed as a street comedian with a suitcase and stand, traveling the college circuit, and performing impromptu skits for gathering crowds.

Hall's first professional work was as a writer and performer on the American sketch comedy TV series Fridays from 1980 until 1982. After the end of Fridays, Hall co-wrote and starred in the satirical comedy series Not Necessarily the News from 1983 until 1990 where he coined the term "sniglet" and collected and published several volumes of books of them. Matt Groening has described him as the inspiration for Moe Szyslak from The Simpsons.^[2] He was also a regular on Saturday Night Live. In 1986, he had his own Showtime channel special, Vanishing America, which was turned into a book with the same title. He hosted a talk show during The Comedy Channel's 1990-91 season, titled Rich Hall's Onion World.

In the United States, he has appeared several times on American talk shows such as Late Show with David Letterman and Late Night with Conan O'Brien.

Appearances and work in the United Kingdom[link]

Outside his homeland, Hall has also achieved popularity in the United Kingdom, where he has lived on-and-off for 23 years. He spends part of his time during the off-seasons writing plays in the United States where he has a small ranch just outside Livingston, Montana. The rest of the time is spent in London, where he owns a flat. Hall is a guest on popular BBC panel quiz shows, most notably as a regular guest on QI,^[3] for which he has received much critical acclaim and is known as the game's most frequently victorious guest panellist with seven victories (only permanent panellist Alan Davies has won more shows), and also with appearances in 8 Out of 10 Cats, Have I Got News for You and Never Mind the Buzzcocks.^[4][5] He has also appeared on the British stand-up comedy series Jack Dee's Live at the Apollo. His appearances achieved some cult status due to his line of jokes on Live at the Apollo about Tom Cruise, and the perceivable similarities between many of his roles. In 2000, he won the Perrier Comedy Award at the Edinburgh Fringe, in the guise of his own grizzled uncle, Otis Lee Crenshaw, the much-convicted country music singer. He has released several albums and a concert movie as this character. In 2004, he published a book of the man's memoirs, entitled Otis Lee Crenshaw: I Blame Society, and in 2007 he finished a screenplay for a film based on the book, written for the director Mel Smith.^[6] In 2006, Hall also wrote and acted in the play Levelland at the Edinburgh Festival.

Hall has had four BBC TV series of his own: Rich Hall's Badly Funded Think Tank, Rich Hall's Fishing Show in 2003, Rich Hall's Cattle Drive in 2006, as well as a one-off programme about the 2004 American Presidential Elections, Rich Hall's Election Special. He also appeared on the BBC Two programme Top Gear, where he successfully managed to make a song about a Rover 25 car, much to the enjoyment of host Jeremy Clarkson and the audience. After the September 11, 2001 attacks, Hall was entrusted with the task of responding to the tragedy on the first subsequent edition of Have I Got News for You.

Hall has written and presented three 90-minute documentaries about film genres, broadcast on BBC Four. Rich Hall's How the West Was Lost (first broadcast June 2008)^[7] discusses Westerns, Rich Hall's The Dirty South (October 2010) challenges stereotypical Hollywood presentations of the Southern United States,^[8][9] and Rich Hall's Continental Drifters (November 2011) examines the American road movie.^[10]

In 2007, he returned to the Fringe with his second play, Best Western, which he wrote and directed. In 2008, Hall toured two stand-up shows around the UK: Rich Hall Autumn Tour 2008 played around 45 dates and he also went on the road as his alter-ego in a show entitled Otis Lee Crenshaw and Band that listed Rich Hall as a "special guest." He subsequently toured a version of this show throughout the UK and Ireland in 2009, with long time sidekick Myron T. Buttram (guitarist and pedal steel player, Rob Childs) and Lonesome Dave (banjoist and guitarist, David Lindsay) appearing at the 2009 Adelaide Fringe festival, the Sydney Opera House, and the 2009 Melbourne Comedy festival. With the band renamed as "The Honky Tonk A**holes" and joined by Horst Furst II (bassist, Nigel Portman Smith) and drummer Mark Hewitt, his autumn 2009 tour included a performance at London's Hammersmith Apollo, which was recorded and released in November 2009 as a live DVD.

In 2009, he performed at the Edinburgh Festival in two shows, his solo stand up and also with long time collaborator Mike Wilmot and Montana-based actor Tim Williams in a new play entitled "Campfire Stories".

On April 5, 2010, Hall appeared as one of the stand-up acts on Channel 4's Comedy Gala, a benefit show organised by Channel 4 to raise money for Great Ormond Street Children's Hospital.

Hall is now a regular performer on Channel 4's Stand Up for the Week, which began in June 2010.^[11]

Other appearances[link]

Hall also made an Irish TV appearance as a guest on the fifth series of RTÉ's topical news comedy programme, Don't Feed the Gondolas, and has appeared at the Kilkenny Cat Laughs comedy festival on 15 occasions. He has also performed at the West Belfast Festival/Feile an Phobail, one of the largest community festivals in Ireland, to a sell-out audience where he received widespread critical acclaim.

Hall appeared in several Pizza Hut commercials in the 1980s, mainly promoting Pizza Hut's guarantee of serving each customer within five minutes.

He has also achieved some popularity in Australia, regularly appearing at the Melbourne International Comedy Festival and the Adelaide Fringe Festival, and also on Australian comedy panel shows, such as The Glass House and Spicks and Specks.

Rich Hall also made a guest appearance on Top Gear (British TV series) in 2003.

Hall has also appeared in France at the Altitude Comedy Festival 2008 in the ski resort of Meribel. He also appeared — albeit briefly — in the 2006 Cheap Seats (ESPNCL) episode titled "Steve Garvey Celebrity Skiing". He was also at the Garvey 1989 Celebrity Ski Classic.

[edit] List of celebrities impersonated on SNL

• Doug Henning
• Doug Flutie
• Bernhard Goetz
• Caspar Weinberger
• Paul Harvey
• David Byrne
• Mark Goodman
• Vince McMahon

Musical and literary career[link]

Discography[link]

1. London Not Tennessee (with The Black Liars) (2001)
2. How Do We Do It? Volume! (2003)

Bibliography[link]

1. 1984: Sniglets (Snig'Lit: Any Word That Doesn't Appear in the Dictionary, but Should), ISBN 0-02-012530-5
2. 1985: More Sniglets: Any Word That Doesn't Appear in the Dictionary, but Should
3. 1986: Unexplained Sniglets of the Universe
4. 1986: Rich Hall's Vanishing America, ISBN 0-02-547480-4
5. 1987: Angry Young Sniglets (1987)
6. 1989: When Sniglets Ruled the Earth (1989)
7. 1994: Self Help for the Bleak: Attaboy Therapy, ISBN 0-8431-3669-3
8. 2002: Things Snowball, ISBN 0-349-11576-1
9. 2003: Top Gear, (2003)
10. 2004: Otis Lee Crenshaw: I Blame Society, ISBN 0-349-11818-3
11. 2009: Magnificent Bastards, ISBN 0-349-11965-1

References[link]

External links[link]

• Rich Hall at the Internet Movie Database
• Rich Hall reading from "Magnificent Bastards" at writLOUD, London