Atomic Number
53
Element 53
Iodine (I)
Iodine is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black nonmetallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius.
Atomic Mass
126.9 u
Category
Halogen
Period
5
Group
Group 17: halogens
Phase
solid
Density
4.933 g/cm3
Electron Shells
2, 8, 18, 18, 7
Atomic Structure
Protons: 53. Electrons: 53. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵
Why Iodine Matters
Iodine helps connect atomic number 53, halogen behavior, period 5 trends, and electron shell structure. Its solid phase, atomic mass of 126.9 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Iodine was discovered 1811 by Bernard Courtois. Iodine is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black nonmetallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius.
Safety and Handling Context
Iodine belongs to the halogen family, where many pure elements are reactive and irritating or toxic at high concentrations. Classroom work should use approved compounds and teacher guidance.
Related Elements
Frequently Asked Questions
- What is the atomic number of Iodine?
- Iodine has atomic number 53, which means a neutral atom has 53 protons and 53 electrons.
- What is the chemical symbol for Iodine?
- The chemical symbol for Iodine is I.
- What category is Iodine in?
- Iodine is classified as a halogen and sits in period 5 of the periodic table.
Explore Iodine in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Iodine to neighboring elements without losing your place.