Electronic data		Thermal data		Steric data
Shells: 2,8,18,18,7 Orbitals: [Kr] 4d10 5s2 5p5 Electronegativity: 2.2, 2.5 1. Ionization potential: 10.4513 eV 2. Ionization potential: 19.131 eV 3. Ionization potential: 33.0 eV Oxidation states: 7,5,1,-1 Electrical conductivity: 8.0e-16 10^6		Melting point: 113.5 °C Boiling point: 184.35 °C Specific heat: 0.214 J/gK Heat of fusion: 7.824 kJ/mol Heat of vaporization: 20.752 kJ/mol Thermal conductivity: 0.00449 W/cmK		Atomic radius: 1.32 Å Ionic radius: 2.20 Å () Covalent radius: 1.33 Å Atomic volume: 25.74 cm³/mol Density (293 K): 4.93 g/cm³ Crystal structure: Orthorhombic

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Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
122I	0	122	1	3.62m	+,EC	View
123I	0	123	5/2	13.2h	EC	View
124I	0	124	2	4.18d	EC,+	View
125I	0	125	5/2	60.1d	EC	View
126I	0	126	2	13.0d	EC,-,+	View
127I	100	126.905	5/2	--	stable	--
128I	0	128	1	25.00m	-,EC,+	View
129I	0	129	7/2	1.57E07y	-	View
130I	0	130	5	12.36h	-	View
131I	0	131	7/2	8.04d	-,b-	View
132I	0	132	4	2.28h	-	View
133I	0	133	7/2	20.8h	-,b-	View
134I	0	134	4	52.6m	-	View
135I	0	135	7/2	6.57h	-,b-	View
136I	0	136	2	1.39m	-	View

Legend

Name origin:	Greek: iôeides (violet colored).
Description:	Shiny, black, non-metalic solid; as a gas it is violet and intensely irritating to the eyes, nose and throat.
Discovered by:	Bernard Courtois
Year:	1811
Place:	France
Sources:	Occurs on land and in the sea in sodium and potassium compounds.
Use(s):	Required in small amounts by humans. Once used as an antiseptic, but no longer due to its poisonous nature.