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53 I Iodine 126.904473

Iodine

DIATOMIC NONMETAL
Bohr Model: Electrons arranged in energy shells around the nucleus.

Iodine is a chemical element with symbol I and atomic number 53. The name is from Greek ἰοειδής ioeidēs, meaning violet or purple, due to the color of iodine vapor. Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers.

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Quick Facts

Atomic Number 53
Period 5
Group 17
Phase Solid
Appearance lustrous metallic gray, violet as a gas
About Diatomic Nonmetals

Diatomic nonmetals naturally exist as molecules of two atoms (e.g., O₂, N₂). They are typically gases at room temperature.

History

Discovered By Bernard Courtois
Named By Unknown

Physical Properties

Atomic Mass 126.904473
Density 4.933 g/L
Molar Heat N/A J/(mol·K)
Phase Transition (Melting & Boiling Points)

Iodine melts at 386.85 K and boils at 457.4 K.

Atomic Properties

Electron Config [Kr] 4d10 5s2 5p5
Electronegativity 2.66
Electron Affinity 295.1531 kJ/mol
Ionization Energy 1008.4 kJ/mol
Orbital Filling Diagram
This diagram visualizes electron configuration according to the Aufbau principle and Hund's rule. Boxes represent orbitals (s, p, d, f), while arrows indicate electrons with spin up or down. Electrons fill lower energy levels first and occupy orbitals singly before pairing.

Photograph

Image of Iodine Source: Wikipedia

External Resources

Wikipedia PubChem Royal Society of Chemistry Periodic Videos (YouTube)

Study Guide

Atomic Number

The number of protons in the nucleus, which defines the element.

Atomic Mass

The average mass of an atom, including protons and neutrons.

Electronegativity

A measure of how strongly an atom attracts electrons in a bond.

Ionization Energy

The energy required to remove an electron from an atom.

Electron Config

The arrangement of electrons in the atom's energy shells.