Iodine is a glossy purple-black solid nonmetal found in its purest form. Let us discuss some iodine facts.
Iodine is within the category of a halogen, which is a group of elements having a high level of chemical reactivity. It has certain metallic properties despite being a nonmetal in theory. It changes from a solid to a gaseous state without effort, releasing a purple vapour in the process.
Let us talk about the chemical characteristics of iodine, such as electronegativity, allotropic forms, oxidation states, period, isotopes, and ionisation energy.
Iodine symbol
Iodine is denoted by the symbol “I” in the periodic table. The word “iodine” has its roots in the Greek word “ioeides,” which translates to “violet coloured.”
Iodine group in periodic table
Iodine is a halogen that is classified in group 17 of the periodic table, sometimes known as 7A (or VIIA).
Iodine period in periodic table
The element iodine belongs to the 5th period of the periodic chart. It can be found in the group’s column below the element bromine and the period’s row between the elements tellurium and xenon.
Iodine block in periodic table
Iodine belongs to the p-block and has a 4p5 electronic configuration structure with 5p-orbital electrons.
Iodine atomic number
Iodine has an atomic number of 53 due to the presence of 53 protons and 53 electrons in its nucleus.
Iodine atomic Weight
The atomic mass/weight of iodine is 126.9 g/mol for Ar°(I). The protons and neutrons of an atom can be added together to get its atomic weight, making it the heaviest among the halogens.
Iodine Electronegativity according to Pauling
Iodine has an electronegativity of 2.66 on the Pauling scale. It has the lowest electronegativity on the Pauling scale of any halogen atom.
Iodine atomic Density
The density of iodine is 4.933 g/cm3. Iodine has a specific gravity of 4.93 at ambient temperature, a solid physical state at 20 °C, and a gas density of 11.27 g/L.
Iodine melting point
Iodine has a melting point of 386.85 K (113.7 °C, 236.66 °F) when it is in the form of I2 molecules.
Iodine boiling point
Iodine has a boiling point of 457.4 K (184.3 °C, 363.7 °F) when it is present as an I2 molecule. Iodine’s boiling point is higher than that of the other halogens as well.
Iodine Vanderwaals radius
Iodine has a van der Waals radius of 198 pm(1pm=1*10‑12 m) or 0.177 nm.
Iodine ionic/covalent radius
Iodine has an ionic radius of 0.05 nm in the (+7) oxidation state and a covalent radius of 139 pm (or 0.128 nm). The coordination ionic centres for iodine are shown in the table below:
| Iodine Ion(In+ ) | Coordinating Structure | Ionic Radius (1pm=1*10‑12 m) |
| I(VII) | 4-coordinate, tetrahedral | 56pm |
| I(-I) | 6-coordinate, octahedral | 206pm |
| I(VII) | 6-coordinate, octahedral | 67pm |
Iodine isotopes
The chemical elements known as isotopes, which have identical nuclei or nuclear charges,
appear in a range of unique types. Let us check the Iodine isotopes now.
There are 37 known isotopes of iodine, with masses ranging from I-108 to I-144. The only isotope with known natural occurrences is iodine-127. Others are radioactive and have half lifetimes that are too short to be primordial. Iodine exhibits monoisotopic and mononuclidic behaviour as a result.
The most prevalent iodine isotopes are listed in the table below:
| Isotope of iodine | Excitation energy | Half-life | Decay Mode | Daughter isotopes |
| 123I | 122.905589 | 13 h | ε, γ | 123Te |
| 124I | 123.9062099 | 4.176 d | ε | 124Te |
| 125I | 124.9046302 | 59.40 d | ε | 125Te |
| 127I | 126.904473 | Stable | Stable | Stable |
| 129I | 128.904988 | 1.57×107 y | β− | 129Xe |
| 131I | 130.9061246 | 8.02070 d | β− γ | 131Xe |
| 135I | 134.910048 | 6.57 h | β− | 135Xe |
Iodine electronic shell
Energy is the level at which an electron corresponds to its electronic shell. Let us count how
many electronic shells there are in iodine.
There are five electronic shells in the iodine electron structure. Each of its electrical shells has 2, 8, 18, 18, and 7 electrons, respectively.
Iodine electron configurations
The electron configuration of an atom or an element refers to how the electrons are arranged within its orbitals/ shell. Let us find the electron configurations in iodine.
Iodine has the following electron configurations: 1s2,2s2,2p6,3s2,3p6,3d10,4s2,4p6,4d10,5s2,5p5 or [Kr] 4d105s25p5. Element of period 5 according to orders 4d, 5s, and 5p are inserted into their shells.
Five of the seven valence electrons in iodine’s electron structure are in the 5p orbital, while two are in the 5s orbital.
Iodine energy of first ionisation
Iodine has a 1st ionisation energy of 1008.4 kJ/mol. I + IE → I++ e– ([Kr] 4d10,5s2,5p5; I→I1+), which has the lowest ionisation energy, must be eliminated from the initial electrons of iodine.
Iodine energy of second ionisation
Iodine has a 2nd ionisation energy of 1845.9 kJ/mol. When an electron is ionised twice, substantially more of it is produced than the first time. I+ + IE → I2+ + e– ([Kr] 4d10,5s2,5p4; I1+→I2+) is the equation.
Iodine energy of third ionisation
Iodine has a 3rd ionisation energy of 3180 kJ/mol. Taking the third electron from the partially occupied p-orbital requires the following steps: ([Kr] 4d10,5s2,5p3; I2+→I3+) I2+ + IE → I3+ + e–. The third ionisation energy is particularly high as a result of I2+(5p3).
Iodine oxidation states
Iodine has an oxidation state of 0 and is a neutral element. It is an extremely acidic oxide and can exist in several oxidation states ranging from -1, +1, +3, +4, +5, +6, and +7 when present in a molecule. Iodide, I–, exhibits the oxidation state (-1) with the greatest frequency among its compounds.
The table below shows the iodine’s oxidation state:
| Iodine compounds | Oxidation states |
| Elemental iodine, I2 | 0 |
| Iodide, I– | -1 |
| Hypoiodite, IO– | +1 |
| Iodite, IO2 | +3 |
| Iodate, IO3– | +5 |
| Periodate, IO4– | +7 |
Iodine CAS number
Iodine’s CAS registry number is 7553-56-2.
Iodine ChemSpider ID
The ChemSpider ID for iodine is 4514549.
Iodine allotropic forms
Allotropes behave physically differently from their chemical equivalents. Let us talk about the allotropy of iodine.
The only allotropic form of iodine is in its molecular form, diiodine.
Iodine chemical classification
Iodine is categorised under many chemical categories in the list below.
- Iodine has a 1.3×107Ω⋅m electrical resistivity at 0 °C.
- Iodine has lesser oxidising power than bromine, chlorine, or fluorine.
- The base-centred orthorhombic crystal structure layers I2 molecules to produce solid iodine.
- Iodine has the highest van der Waals interactions among the halogens because it has the largest electron cloud among them which is also the easiest to polarise.
Iodine state at room temperature
Iodine is a solid at room temperature due to its huge molecular weight and powerful Van Der Waals forces. It is a nonmetallic, almost-black solid with a sparkling crystalline look.
Is Iodine paramagnetic?
When a weak external magnetic field is applied, some materials exhibit paramagnetism, a
type of magnetism. Let us find out if iodine has a magnetic property or not.
Iodine is diamagnetic and possesses one unpaired electron in its elemental state. Iodine has a molar magnetic susceptibility of −88.7×10−6 cm3/mol at 298 K.
Iodine has the highest van der Waals interactions among the halogens because it has the largest electron cloud among them which is also the easiest to polarise.
Conclusion
The natural quantity of iodine in the crust of the Earth is 0.000049%. It can be discovered naturally in food, seaweed, petroleum deposits, and caliche ore deposits. It is violet in colour and extremely irritating to the eyes, nose, and throat when it acts as a gas.
Read more about the following chemical properties.
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