Iodine (I)
Iodine is the 53rd element, a halogen in the p-block. Its standard atomic weight is 126.904.
Iodine
126.904
What the table records
- Atomic number
- 53
- Standard atomic weight
- 126.904
- Group
- 17
- Period
- 5
- Block
- p-block
- Category
- Halogen
- [Kr] 4d10 5s2 5p5
- Valence electrons
- 7
- Typical valence
- 1
- Van der Waals radius
- 2.1 Å
- Covalent radius
- 1.39 Å
Molecules containing iodine
The lightest named structures in this library that contain I.
Atomic iodine
I · 126.9 g/mol
Iodide Ion
I- · 126.9 g/mol
Iodine(1+)
I+ · 126.9 g/mol
Hydrogen iodide
HI · 127.91 g/mol
Methyl iodide
CH₃I · 141.94 g/mol
Sodium Iodide
INa · 149.89 g/mol
EtI
C₂H₅I · 155.97 g/mol
Iodine chloride
ClI · 162.36 g/mol
Iodoacetonitrile
C₂H₂IN · 166.95 g/mol
Allyl iodide
C₃H₅I · 167.98 g/mol
Isopropyl iodide
C₃H₇I · 169.99 g/mol
PrI
C₃H₇I · 169.99 g/mol
How to read these numbers
The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.
The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.