53 I Iodine 126.9 u

Iodine

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Period
5
Group
17
Block
p-block
Phase (STP)
Solid

Iodine is a halogen essential for thyroid function. It sublimes to form a purple vapor and is used as a disinfectant.

About Iodine

Iodine (I) is a halogen essential to human health, required by the thyroid gland to synthesize hormones that regulate metabolism. Element 53 sits in group 17 of period 5 in the p-block, with an atomic mass of 126.9, the electron configuration [Kr] 4d¹⁰ 5s² 5p⁵, and a high Pauling electronegativity of 2.66. Solid at standard conditions, it readily sublimes to a violet vapor, a behavior unusual among the elements. Iodine and its solutions are valued as antiseptics and disinfectants, and it is the heaviest of the common, stable halogens, sitting below chlorine and bromine in the group.

Physical Properties

Atomic Mass 126.9 u
Phase at STP Solid

Electronic Properties

Electronegativity 2.66

Electron Configuration

Configuration [Kr] 4d¹⁰ 5s² 5p⁵

Electron Shell Configuration

Iodine electron shell configuration I 2e⁻ 8e⁻ 18e⁻ 18e⁻ 7e⁻

Position in Periodic Table

Iodine position in the periodic table I

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving I

Beta Decay of Iodine-131

¹³¹I → ¹³¹Xe + e⁻ + ν̄ₑ + γ

Nuclear

Chlorine Displacing Iodine from Potassium Iodide

Cl₂ + 2KI → 2KCl + I₂

Single-Replacement

Hydrogen Peroxide as Oxidizing Agent (Acidic)

H₂O₂ + 2H⁺ + 2I⁻ → I₂ + 2H₂O

Redox

Iodine and Sodium Thiosulfate Titration

I₂ + 2Na₂S₂O₃ → Na₂S₄O₆ + 2NaI

Redox

Vitamin C as Reducing Agent

C₆H₈O₆ + I₂ → C₆H₆O₆ + 2HI

Redox

Compounds Containing Iodine

Periodic Acid

HIO₄

Potassium Iodate

KIO₃

Potassium Iodide

KI

Sodium Periodate

NaIO₄

More Halogen

9 F Fluorine 17 Cl Chlorine 35 Br Bromine 85 At Astatine

Frequently Asked Questions

What is Iodine?
Iodine (I) is a chemical element with atomic number 53. It is a solid at standard temperature and pressure, classified as a halogen.
What are the key properties of Iodine?
Iodine has an atomic mass of 126.9 u.
What is the electron configuration of Iodine?
The electron configuration of Iodine is [Kr] 4d10 5s2 5p5. It is in the p-block of the periodic table.
What is the electronegativity of Iodine?
Iodine has an electronegativity of 2.66 on the Pauling scale.