Mendelevium (pronounced men-deh-LEE-vi-em) is an artificially produced, radioactive element with the symbol Md and the atomic number 101. Mendelevium is a metallic, radioactive, transuranic element of the actinides. The actinides are the elements located in the bottom row of the periodic table, having atomic numbers 89 through 103. A transuranic element is one that has a higher atomic number than uranium, these are man made and not found in nature. Mendelevium is synthesized by bombarding einsteinium with helium ions. This element was named after Dmitri Mendeleev, who devised one form of the Periodic Table.

Previous Element: Fermium Next Element: Nobelium	101 Md 256.1
Physical Properties
Color	---
Phase at Room Temp.	---
Density (g/cm3)	---
Hardness (Mohs)	---
Melting Point (K)	1100K
Boiling Point (K)	---
Heat of Fusion (kJ/mol)	---
Heat of Vaporization (kJ/mol)	---
Heat of Atomization (kJ/mol)	---
Thermal Conductivity (J/m sec K)	---
Electrical Conductivity (1/mohm cm)	---
Source	Synthetic
Atomic Properties
Electron Configuration	[Rn]7s25f13
Number of Isotopes	19 (0 natural)
Electron Affinity (kJ/mol)	---
First Ionization Energy (kJ/mol)	635
Second Ionization Energy (kJ/mol)	---
Third Ionization Energy (kJ/mol)	---
Electronegativity	1.3
Polarizability (Å3)	18.2
Atomic Weight	256.1
Atomic Volume (cm3/mol)	---
Ionic Radius2- (pm)	---
Ionic Radius1- (pm)	---
Atomic Radius (pm)	---
Ionic Radius1+ (pm)	---
Ionic Radius2+ (pm)	---
Ionic Radius3+ (pm)	---
Common Oxidation Numbers	+3
Other Oxid. Numbers	+2
Abundance
In Earth's Crust (mg/kg)	---
In Earth's Ocean (mg/L)	---
In Human Body (%)	---
Regulatory / Health
CAS Number	7440-11-1
OSHA Permissible Exposure Limit (PEL)	No limits
OSHA PEL Vacated 1989	No limits
NIOSH Recommended Exposure Limit (REL)	No limits
Sources: University of Wisconsin General Chemistry Mineral Information Institute Jefferson Accelerator Laboratory EnvironmentalChemistry.com

Characteristics

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 isotope ²⁵⁶Md has been used to find out some of the chemical properties of mendelevium, but it has no other uses outside of basic scientific research. Only trace amounts of the element have ever been produced. All isotopes of mendelevium that have been discovered are radioactive. Other isotopes range from 245 to 262 mass numbers, and have half-lives from a few seconds to about 51.5 days. The original ²⁵⁶Md had a half-life of 77 minutes. It is assumed that mendelevium’s standard state is solid at 298K, and its classification is metallic.

History

Mendelevium was first produced by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey, and Stanley G. Thompson in 1955 at the University of California, Berkeley. The team produced ²⁵⁶Md when they bombarded an ²⁵³Es target with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory’s 60-inch cyclotron (²⁵⁶Md was the first element to be synthesized one-atom-at-a-time). 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.

Isotopes

Fourteen isotopes of mendelevium 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. The isotope ²⁵⁸Md undergoes two different forms of radioactive decay, causing it to have two different half-lives, one of 57 minutes and one of 51.5 days.

Further Reading

• Los Alamos National Laboratory - Mendelevium lanl.org. 2003. Accessed on-line: 9/21/2009
•  Steve Gagnon. It's Elemental - Mendelevium. Jefferson Lab. 2009. Accessed on-line: 9/21/2009
• Mark Winter. Mendelevium - WebElements.com. 1993 - 2009. Accessed on-line: 9/21/2009
• Kenneth Burbalace. Periodic Table of Elements - Mendelevium - Md. EnvironmentalChemistry.com. 1995 - 2009. Accessed on-line: 9/21/2009
• National Nuclear Data Center. NuDat 2.5. 2009. Accessed on-line: 9/17/2009
• The New Encyclopedia Britannica. 15th Edition, 2007. Volume 8. pp 5. 

 

Note: This article uses material from the Wikipedia article Mendelevium that was accessed on August 25, 2009. The Author(s) and Topic Editor(s) associated with this article may have significantly modified the content derived from Wikipedia with original content or with content drawn from other sources. All content from Wikipedia has been reviewed and approved by those Author(s) and Topic Editor(s), and is subject to the same peer review process as other content in the EoE. The current version of the Wikipedia article may differ from the version that existed on the date of access. This article is licensed under the GNU Free Documentation License 1.2. See the EoE’s Policy on the Use of Content from Wikipedia for more information.

Mendelevium (pronounced men-deh-LEE-vi-em) is an artificially produced, radioactive element with the symbol Md and the atomic number 101. Mendelevium is a metallic, radioactive, transuranic element of the actinides. The actinides are the elements located in the bottom row of the periodic table, having atomic numbers 89 through 103. A transuranic element is one that has a higher atomic number than uranium, these are man made and not found in nature. Mendelevium is synthesized by bombarding einsteinium with helium ions. This element was named after Dmitri Mendeleev, who devised one form of the Periodic Table.

Previous Element: Fermium Next Element: Nobelium	101 Md 256.1
Physical Properties
Color	---
Phase at Room Temp.	---
Density (g/cm3)	---
Hardness (Mohs)	---
Melting Point (K)	1100K
Boiling Point (K)	---
Heat of Fusion (kJ/mol)	---
Heat of Vaporization (kJ/mol)	---
Heat of Atomization (kJ/mol)	---
Thermal Conductivity (J/m sec K)	---
Electrical Conductivity (1/mohm cm)	---
Source	Synthetic
Atomic Properties
Electron Configuration	[Rn]7s25f13
Number of Isotopes	19 (0 natural)
Electron Affinity (kJ/mol)	---
First Ionization Energy (kJ/mol)	635
Second Ionization Energy (kJ/mol)	---
Third Ionization Energy (kJ/mol)	---
Electronegativity	1.3
Polarizability (Å3)	18.2
Atomic Weight	256.1
Atomic Volume (cm3/mol)	---
Ionic Radius2- (pm)	---
Ionic Radius1- (pm)	---
Atomic Radius (pm)	---
Ionic Radius1+ (pm)	---
Ionic Radius2+ (pm)	---
Ionic Radius3+ (pm)	---
Common Oxidation Numbers	+3
Other Oxid. Numbers	+2
Abundance
In Earth's Crust (mg/kg)	---
In Earth's Ocean (mg/L)	---
In Human Body (%)	---
Regulatory / Health
CAS Number	7440-11-1
OSHA Permissible Exposure Limit (PEL)	No limits
OSHA PEL Vacated 1989	No limits
NIOSH Recommended Exposure Limit (REL)	No limits
Sources: University of Wisconsin General Chemistry Mineral Information Institute Jefferson Accelerator Laboratory EnvironmentalChemistry.com

Characteristics

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 isotope ²⁵⁶Md has been used to find out some of the chemical properties of mendelevium, but it has no other uses outside of basic scientific research. Only trace amounts of the element have ever been produced. All isotopes of mendelevium that have been discovered are radioactive. Other isotopes range from 245 to 262 mass numbers, and have half-lives from a few seconds to about 51.5 days. The original ²⁵⁶Md had a half-life of 77 minutes. It is assumed that mendelevium’s standard state is solid at 298K, and its classification is metallic.

History

Mendelevium was first produced by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey, and Stanley G. Thompson in 1955 at the University of California, Berkeley. The team produced ²⁵⁶Md when they bombarded an ²⁵³Es target with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory’s 60-inch cyclotron (²⁵⁶Md was the first element to be synthesized one-atom-at-a-time). 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.

Isotopes

Fourteen isotopes of mendelevium 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. The isotope ²⁵⁸Md undergoes two different forms of radioactive decay, causing it to have two different half-lives, one of 57 minutes and one of 51.5 days.

Further Reading

• Los Alamos National Laboratory - Mendelevium lanl.org. 2003. Accessed on-line: 9/21/2009
•  Steve Gagnon. It's Elemental - Mendelevium. Jefferson Lab. 2009. Accessed on-line: 9/21/2009
• Mark Winter. Mendelevium - WebElements.com. 1993 - 2009. Accessed on-line: 9/21/2009
• Kenneth Burbalace. Periodic Table of Elements - Mendelevium - Md. EnvironmentalChemistry.com. 1995 - 2009. Accessed on-line: 9/21/2009
• National Nuclear Data Center. NuDat 2.5. 2009. Accessed on-line: 9/17/2009
• The New Encyclopedia Britannica. 15th Edition, 2007. Volume 8. pp 5. 

 

Note: This article uses material from the Wikipedia article Mendelevium that was accessed on August 25, 2009. The Author(s) and Topic Editor(s) associated with this article may have significantly modified the content derived from Wikipedia with original content or with content drawn from other sources. All content from Wikipedia has been reviewed and approved by those Author(s) and Topic Editor(s), and is subject to the same peer review process as other content in the EoE. The current version of the Wikipedia article may differ from the version that existed on the date of access. This article is licensed under the GNU Free Documentation License 1.2. See the EoE’s Policy on the Use of Content from Wikipedia for more information.