Iodine

Main page

Chemistry • Periodic table • Polymers • Organic compounds • Inorganic compounds • R/S-phrases

Education • Main page • Innovation in R&D

The site • Disclaimer • About the site • Site history

Other names/abbreviations:

I

Element no:	53
Element group:	17 (IUPAC) VII A (American labelling) VII B (European labelling) Halogens
Element type:	Nonmetals
CAS-Number:	7553-56-2
EINECS-Number:	231-442-4

Chemical properties

Reaction of iodine with metals/metal ions
Solid Cd does not react with I₂ (g), but will react with I₂ (aq). In gas phase Cd and I₂ will react forming CdI₂. At high temperature and pressure (e.g. a steel bomb) equivalent Cd and I₂ will react forming CdI [4].

Cd (s) + I₂ (aq) Cd²⁺ (aq) + 2 I^- (aq)
Cd (g) + I₂ (g) CdI₂ (g)
2 Cd (g) + I₂ (g) 2CdI (g)


Manganese with oxidation steps >2 will be reduced to Mn(II) by I^- under acidic conditions under the formation of I₂, e.g.

MnO₂ (s) + 2 I^- (aq) + 4 H⁺ (aq) Mn²⁺ (aq) + I₂ (aq) + 2 H₂O (l)


Solubility
Water: 0.3 g/L (20 °C) [2]

Safety

Symbol: Xn
R-phrases: 20/21
S-phrases: 23-25

Physical properties

Appearance
	Physical state @ 20°C:	Solid [1]
	Color:	Solid: Black [1] Gas: Violet [1]
	Odor:	Pungent [2]

Bulk properties
	Molecular weight (g/mol):	126.90447(3) [1]
	Melting point (°C):	113.6 [1]
	Boiling point (°C):	185.2 (sublimation) [1]
	Density (g/cm3):	4.93 (20 °C) [2]

Optical properties
	Refractive index:	3.34 [3]

Thermodynamic properties
	ΔfH°gas (kJ/mol):	106.8 (monoatomic) [3] 62.4 (I2) [3]
	ΔfH°solid (kJ/mol):	0.0 (I2, rhombic) [3]
	ΔH°fusion (kJ/mol):	15.52 (I2) [3]
	S°gas (J/K·mol):	180.8 (monoatomic) [3] 260.7 (I2) [3]
	S°solid (J/K·mol):	116.1 (I2) [3]
	ΔfG°gas (kJ/mol):	70.2 (monoatomic) [3] 19.3 (I2) [3]
	Cp (gas) (J/K·mol):	20.8 (monoatomic, 25 °C) [3] 36.9 (I2, 25 °C) [3]
	Cp (solid) (J/K·mol):	54.4 (I2, rhombic, 25 °C) [3]
	Critical temperature (°C):	546 [3]

Electronic properties
	Electron configuration:	1s2-2s2-2p6-3s2-3p6-3d10-4s2-4p6-4d10-5s2-5p5
	Ionic radius (Å):	2.20 [1]
	Electron affinity [M-M-] (kJ/mol):	295.3 [1]

Misc.
	Vapour pressure (Pa):	28 (20 °C) [2]

References

1: Greenwood,N.N., Earnshaw,A. Chemistry of the elements
2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain

2: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5

3: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA

4: Gmelin Handbuch der anorganischen Chemie Erg. 33 (1958)

---

© Michael Pilgaard
Created: October 2, 2008
Last update: October 10, 2008