Iodine (I)
Iodine is the heaviest element that the human body is known to need.
Iodine properties
- Atomic mass
- 126.9 u
- Category
- Halogen
- Group
- 17
- Period
- 5
- Block
- p-block
- State at room temp.
- Solid
- Electronegativity
- 2.66
- Melting point
- 386.85 K (113.7 °C)
- Boiling point
- 457.4 K (184.2 °C)
- Density
- 4.933 g/cm³
- Oxidation states
- +7, +5, +1, −1
- Atomic radius
- 198 pm
- Ionization energy
- 10.451 eV
- Electron affinity
- 3.059 eV
- Radioactive
- No, has stable isotopes
- Discovered
- 1811
Iodine electron configuration
- Electron configuration
- [Kr] 4d10 5s2 5p5
- Full electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p5
- Electron shells
- 2 · 8 · 18 · 18 · 7
The electron configuration of Iodine (I) is [Kr] 4d10 5s2 5p5. Its 53 electrons are arranged in shells as 2, 8, 18, 18, 7.
Protons, neutrons and electrons in Iodine
A neutral Iodine atom has 53 protons and 53 electrons. Most Iodine atoms have about 74 neutrons: the atomic mass rounded to 127, minus the atomic number 53.
Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass
How many valence electrons does Iodine have?
7
Iodine has 7 valence electrons in its outermost shell, shell 5. These are the electrons involved in chemical bonding.
Iodine orbital diagram
Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations
Molar mass of Iodine
126.9 g/mol
One mole of Iodine atoms (6.022 × 10²³ atoms) has a mass of 126.9 grams. Use this value to convert between grams and moles.
Compounds containing Iodine
Iodine facts
- Iodine is the heaviest element that the human body is known to need.
- Iodine turns starch a deep blue-black, which makes it a simple test for starch in foods and school laboratories.
- Iodine (I) has atomic number 53 and is a solid at room temperature. It was discovered in 1811.
Position in the periodic table
Iodine is element 53, in period 5 and group 17 of the periodic table, in the p-block.
Uses of Iodine
Iodine is added to table salt to prevent iodine deficiency, because the thyroid gland needs it to make hormones. Iodine solutions and povidone-iodine are common antiseptics for cleaning skin and wounds. Iodine compounds are used as X-ray contrast agents, in the polarizing films of LCD screens, and as industrial catalysts, while radioactive iodine-131 is used to treat some thyroid conditions and cancers.
Who discovered Iodine?
French chemist Bernard Courtois discovered iodine in 1811 while extracting chemicals from seaweed ash to make saltpeter, when adding sulfuric acid released a violet vapor. Its name comes from the Greek iodes, meaning 'violet'.
Where does the name come from?
Iodine comes from the Greek iodes, meaning 'violet-colored'. Joseph Louis Gay-Lussac proposed the name in 1813 after the striking violet vapor that rises when the element is heated.
Same group
Compare Iodine
FAQ
What is the electron configuration of Iodine?
The electron configuration of Iodine (I) is [Kr] 4d10 5s2 5p5. Its 53 electrons are arranged in shells as 2, 8, 18, 18, 7.
How many protons, neutrons and electrons does Iodine have?
A neutral Iodine atom has 53 protons and 53 electrons. Most Iodine atoms have about 74 neutrons: the atomic mass rounded to 127, minus the atomic number 53.
How many valence electrons does Iodine have?
Iodine has 7 valence electrons in its outermost shell, shell 5. These are the electrons involved in chemical bonding.
What is the molar mass of Iodine?
The molar mass of Iodine is 126.9 g/mol. This is the same number as its atomic mass, 126.9 u.
Is Iodine a metal?
No. Iodine is a halogen, so it is a nonmetal.
Is Iodine radioactive?
Ordinary Iodine is not radioactive: it has at least one stable isotope. Like every element, it also has radioactive isotopes, most of them made in laboratories.
Where is Iodine on the periodic table?
Iodine is element 53, in period 5 and group 17 of the periodic table, in the p-block.