Periodic Table of Elements

02/05/09

Np

Neptunium

Atomic Number

93

Atomic Symbol

Np

Name

Neptunium

	Meaning	Named for the planet Neptune because it was next beyond Uranus
	Group	Rare earth

Atomic Weight

237

Density, g/cubic cm at STP

20.25

Melting Point, °C

640

Boiling Point, °C, 1 atm

4000

Naturally Occurring Isotopes

None

Discoverer

McMillan and Abelson

Year

1940

Ionization Energy, eV

6.2657

Configuration

[Rn] 5f4 6d 7s2

Description

Man-made element synthesized from uranium

References: Holden, Norman E. (March 30, 2004). "History of the origin of the chemical elements and their discoverers." National Nuclear Data Center. Retrieved October 7, 2005 from http://www.nndc.bnl.gov/content/elements.html "List of elements by boiling point." (September 22, 2005). Wikipedia. Retrieved October 9, 2005 from http://en.wikipedia.org/wiki/List_of_elements_by_boiling_point "List of elements by density." (September 22, 2005). Wikipedia. Retrieved October 9, 2005 from http://en.wikipedia.org/wiki/List_of_elements_by_density "List of elements by melting point." (September 22, 2005). Wikipedia. Retrieved October 9, 2005 from http://en.wikipedia.org/wiki/List_of_elements_by_melting_point "NIST chemistry webBook." (2005). National Institute of Standards and Technology. Retrieved October 6, 2005 from http://webbook.nist.gov/chemistry/ Zucker, M.A.; Kishore, A. R.; Sukumar, R.; and Dragoset, R. A. (July 2005). "Elemental data index."  National Institute of Standards and Technology. Retrieved October 7, 2005 from http://physics.nist.gov/PhysRefData/Elements/cover.html