I
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. It has a standard atomic weight of 126.9, sits in period 5 and group 17, and is classified as a halogen.
Properties
| Symbol | I |
|---|---|
| Atomic number | 53 |
| Standard atomic weight | 126.9 |
| Category | Halogen |
| Group | 17 |
| Period | 5 |
| Electron configuration | [Kr] 4d10 5s2 5p5 |
| Outer-shell electrons | 7 |
The figure of 126.9 is a standard atomic weight.
Compounds containing iodine
5 of the compounds in this reference contain I, listed by the fraction of their mass it makes up.
| Compound | Formula | Atoms | % by mass |
|---|---|---|---|
| potassium iodide | IK | 1 | 76.4% |
| levothyroxine | C15H11I4NO4 | 4 | 65.3% |
| thyroxine | C15H11I4NO4 | 4 | 65.3% |
| sodium periodate | INaO4 | 1 | 59.3% |
| potassium iodate | IKO3 | 1 | 59.3% |
Calculate with iodine
- Molar mass of any formula containing it
- Electron configuration, including ions
- Effective nuclear charge by Slater's rules
- Average atomic mass from isotope abundances
Group 17
Atomic weights are the IUPAC 2021 standard values, abridged to the conventional five significant figures. Group, period, category and electron configuration are derived from the atomic number rather than stored, so they cannot drift out of step with it.