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Information valid for I-127 unless otherwise noted

Basic Information

Symbol: I
Atomic Number: 53
Mass: 126.904
Melting Point: 113.5
Boiling Point: 184
Number of Protons/Electrons: 53
Number of Neutrons: 74
Classification: Halogen
Crystal Structure: Orthorhombic
Density: 4.93
Color: blackish

Atomic Structure

[Bohr Model of Iodine]
Number of Energy Levels: 5

  1. First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 18
    Fourth Energy Level: 18
    Fifth Energy Level: 7


Isotope Half Life
I-122 3.6 minutes
I-123 13.2 hours
I-124 4.2 days
I-125 60.1 days
I-126 13 days
I-127 Stable
I-128 25 minutes
I-129 1.57e+007 years
I-130 12.4 hours
I-131 8 days
I-132 2.3 hours
I-133 20.8 hours
I-134 52.6 minutes
I-135 6.6 hours
I-136 1.4 minutes


Date of Discovery: 1804
Discoverer: Bernard Courtois
Name Origin: From the Greek word i˘des (violet)
Uses: required in humans
Obtained From: sodium and potassium compounds