Iodine occurs in compounds in seawater and living things.
Uses and research
Solid iodine can produce a violet vapor when heated.
Elements and compounds behave differently
Halogens occupy group 17. Many familiar materials contain compounds of these elements, but a compound does not inherit all the properties of the pure element. Chloride ions in salt are different from chlorine gas. Even within one group, physical states and chemical behavior vary.
What the atomic number tells us
Iodine has atomic number 53. This is the number of protons in its nucleus. A neutral atom also has 53 electrons. Losing or gaining electrons makes an ion; it does not change the element unless the proton count changes.
The model's rings help count electrons by shell. They are not actual circular paths. A model of one atom and the properties of a whole material are different levels of description.
Temperature and state
25°C: Solid
Illustrative particle motion: sizes, distances and speeds are not to scale. Particles represent atoms or molecules.
← CoolHeat →
Melting point 113.7°C / Boiling point 184.4°C
Pure element at 1 atmosphere. Image conditions are explained in captions. Pictures do not change with temperature.