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Periodic table · chemistry · physics
Element story

Iodine

Atomic number 53 means that every Iodine nucleus contains 53 protons. That proton count is the element's identity: change it and you no longer have Iodine.

Start with the nucleus

Atomic number 53 means that every Iodine nucleus contains 53 protons. That proton count is the element's identity: change it and you no longer have Iodine.

Iodine (I) is chemical element 53. It belongs to the halogens, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

In practice, it turns up most often in thyroid function and nutrition, antiseptics and photography.

See the atom

Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.

What this number means

Atomic number 53 means that every Iodine nucleus contains 53 protons. That proton count is the element's identity: change it and you no longer have Iodine.

Keep exploring

→ Iodine · Atomic structure · Periodic trends

53IIodine
Iodine · I · Z = 53

Iodine (I) is chemical element 53. It belongs to the halogens, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

Understanding the element

Iodine (I) is chemical element 53. It belongs to the halogens, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

Where do we encounter it?

In practice, it turns up most often in thyroid function and nutrition, antiseptics and photography.

What its position in the table tells us

Iodine sits in period 5, group 17 and the P block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.