Element Properties:53-59 atomic number



Atomic symbol: I

Atomic weight: 126.90447

Atomic number: 53

Electron configuration: 2-8-18-18-7

Oxidation states: ±1, +5, 7

State of matter: solid


Discovered in 1811 by Bernard Courtois

Boils at 184°C, melts at 113.5°C


Iodine is bluish-black in color with a metallic luster, characteristic odor, and sharp acrid taste. At room temperature, iodine sublimes into a violet vapor that irritates the eyes, nose, and throat. It dissolves in alcohol and partially in water to make a brown colored solution.


Atomic symbol: Xe

Atomic weight: 131.29

Atomic number: 54

Electron configuration: 2-8-18-18-8

Oxidation states: +0

State of matter: gas

Noble gas

Discovered in 1898 by Sir William Ramsay and Morris W. Travers

Boils at -107.1°C, melts at -111.9°C


Xenon is a colorless, odorless, tasteless relatively inert, monatomic gas. It is heavy and extremely rare. It is inert, meaning it does not react with other elements and has an octet atomic structure. Xenon flash lamps are used to activate ruby lasers. It is the first noble gas to combine with other elements, which was discovered in 1962 by Neil Bartlet, which was previously thought to be impossible.


Atomic symbol: Cs

Atomic weight: 132.9054519

Atomic number: 55

Electron configuration: 2-8-18-18-8-1

Oxidation states: +1

State of matter: solid

Light metal

Discovered in 1860 by Robert Bunsen and Gustav Kirchhoff

Boils at 671°C, melts at 28.5°C


Cesium was the first element to be discovered spectroscopically. It is a silvery-white metal that is extremely reactive and becomes a liquid in warmer atmospheres. Cesium causes an explosive reaction when dropped in water. It has also been used for the construction and operation of a type of atomic clock.


Atomic symbol: Ba

Atomic weight: 137.327

Atomic number: 56

Electron configuration: 2-8-18-8-18-5

Oxidation states: +2

State of matter: solid

Light metal

Discovered in 1808 by Sir Humphry Davy

Boils at 1640°C, mlts at 725°C


Barium    is    used    in   metallurgy,    pyrotechnics, radiology and petroleum mining. It has a silvery-white luster when cut. Like many other light elements, it is very reactive, and it displaces hydrogen in water to form barium hydroxide.


Atomic symbol: La

Atomic weight: 138.9047

Electron configuration: 2-8-18-32-9-2

Atomic number: 57

Oxidation states: +3

State of matter: solid

Heavy metal, brittle

Discovered in 1839 by Carl Gustaf Mosander

Boils at 3454°C, melts at 920°C


Lanthanum is a ductile, malleable, silvery white rare earth metal. It forms alloys with several other metals, and has three allotropic forms. At 268°C Lanthanum becomes a superconductor.


Atomic symbol: Ce

Atomic weight: 140.116

Atomic number: 58

Electron configuration: 2-8-18-20-8-2

Oxidation states: +3, +4

State of matter: solid

Heavy metal, brittle

Discovered in 1803 by Jöns Jacob Berzelius and Wilhelm Hisinger

Boils at 3257°C, melts at 798°C Notes:

Cerium is an iron grayish color that is about as soft and ductile as tin. It is used in metallurgy as stabilizers in alloys, in glass as a polishing agent, in ceramics as an opacifying and strengthening agent, and has many other applications.



Atomic symbol: Pr

Atomic weight: 140.90765

Atomic number: 59

Electron configuration: 2-8-18-21-8-2

Oxidation states: +3

State of matter: solid

Heavy metal, brittle

Discovered in 1885 by Carl Auer von Welsbach

Boils at 3212°C, melts at 931°C


Praseodymium is a silver, moderately soft, ductile, and malleable metal. Small amounts of praseodymium are used in a rare-earth alloy used to make cigarette lighter flints and high strength low-creep magnesium alloys used for jet-engine parts.