Chemical element · Atomic number 53
Iodine
Iodine in the periodic table: atomic number 53, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Halogen
solid
126.9045 u
A locally stored, license-verified sample photograph has not been curated yet.
Atomic classification
Shell occupancy
Iodine in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 18 electrons
- O · n=5
- 7 electrons
- Electron configuration
- [Kr]5s2 4d10 5p5
- Electrons per shell
- 2 · 8 · 18 · 18 · 7
- Group
- 17
- Period
- 5
- Block
- P
- Element category
- Halogen
Go from looking up chemistry to remembering it.
Turn your notes into source-backed study cards and review them at the right time.
Starter stays free · no payment details
Physical and chemical properties
- Atomic mass
- 126.9045 u
- Standard state
- solid
- Density
- 4.93 g/cm³
- Melting point
- 386.85 K
- Boiling point
- 457.55 K
- Electronegativity
- 2.66 (Pauling)
- First ionisation energy
- 10.451 eV
- Oxidation states
- +7, +5, +1, -1
- Discovery
- 1811
Safety and periodic classification
Safety
Safe handling cannot be inferred from Iodine's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Iodine is in period 5, group 17 and the P block. Its direct neighbours by atomic number are Tellurium and Xenon. The recorded Pauling electronegativity is 2.66. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.