Praseodymium (Pr)

Atomic Number: 59

Relative Atomic Mass: 140.90765

Electronegativity: 1.13

Atomic Radius (Picometers): 185

Appearance: Grey-White

Occurrence: Natural

Melting Point (Kelvin): 1208

Boiling Point (Kelvin): 3793

Stable Isotopes: 141

Discoverers: Carl Auer von Welsbach in 1885

Properties: Soft, Ductile, Malleable

First Use: Glass Colourisation (1920s)

Modern Uses: Aircraft Engines, Fire Starters

Picture Courtesy of Jurii

©2011 Grant Dwyer

Cerium (Ce)

Atomic Number: 58

Relative Atomic Mass: 140.116

Electronegativity: 1.12

Atomic Radius (Picometers): 185

Appearance: Silver-White

Occurrence: Natural

Melting Point (Kelvin): 1068

Boiling Point (Kelvin): 3716

Stable Isotopes: 136, 138, 140

Discoverers: Wilhelm Hisinger, Jons Berzelius and Martin Klaproth in 1803

Properties: Soft, Ductile, Malleable

First Use: Unknown

Modern Uses: Catalytic Converters, Optical Polishing 

Picture Courtesy of images-of-elements.com

©2011 Grant Dwyer

Lanthanum (La)

Atomic Number: 57

Relative Atomic Mass: 138.90547

Electronegativity: 1.10

Atomic Radius (Picometers): 195

Appearance: Silver-White

Occurrence: Natural

Melting Point (Kelvin): 1193

Boiling Point (Kelvin): 3737

Stable Isotopes: 139

Discoverer: Carl Mosander in 1838

Properties: Malleable, Soft, Ductile

First Use: Gas Lanterns (1885)

Modern Uses: Batteries, Vacuum Tubes

Picture Courtesy of Jurii

©2011 Grant Dwyer

Barium (Ba)

Atomic Number: 56

Relative Atomic Mass: 137.33

Electronegativity: 0.89

Atomic Radius (Picometers): 215

Appearance: Silver-Grey

Occurrence: Natural

Melting Point (Kelvin): 1000

Boiling Point (Kelvin): 2170

Stable Isotopes: 130, 132, 134, 135, 136, 137, 138

Discoverer: Sir Humphry Davy in 1808

Properties: Soft

First Use: Unknown

Modern Uses: Electroceramics, Bleaching Agent

Picture Courtesy of Matthias Zepper

©2011 Grant Dwyer

Caesium (Cs)

Atomic Number: 55

Relative Atomic Mass: 132.90545192

Electronegativity: 0.79

Atomic Radius (Picometers): 260

Appearance: Silver-Gold

Occurrence: Natural

Melting Point (Kelvin): 301.59

Boiling Point (Kelvin): 944

Stable Isotopes: 133

Discoverer: Robert Bunsen in 1860

Properties: Soft, Ductile

First Use: Chemical and Electric Fields (Unknown)

Modern Uses: Atomic Clock, Centrifugation Fluids

Picture Courtesy of Dnn87

©2011 Grant Dwyer

Xenon (Xe)

Atomic Number: 54

Relative Atomic Mass: 131.2936

Electronegativity: 2.60

Atomic Radius (Picometers): Unknown

Appearance: Colourless (Blue when subjected to a High Voltage Electric Field)

Occurrence: Natural

Melting Point (Kelvin): 161.4

Boiling Point (Kelvin): 165.03

Stable Isotopes: 124, 126, 128, 129, 130, 131, 132, 134, 136

Discoverer: Sir William Ramsay in 1898

Properties: Colourless, Odorless, Heavy, Inert

First Use: High Speed Photography (1930s)

Modern Uses: Lasers, Medical

Picture Courtesy of Alchemist-hp

©2011 Grant Dwyer

Iodine (I)

Atomic Number: 53

Relative Atomic Mass: 126.90447

Electronegativity: 2.66

Atomic Radius (Picometers): 140

Appearance: Grey (Violet when Gas)

Occurrence: Natural

Melting Point (Kelvin): 386.85

Boiling Point (Kelvin): 457.4

Stable Isotopes: 127

Discoverer: Bernard Courtois in 1811

Properties: Low Toxicity, Irritating Odor

First Use: Unknown

Modern Uses: Medical, Water Treatment

Picture Courtesy of Tomihahndorf

©2011 Grant Dwyer