Study Guides/Chemistry/Valency of Iodine
Study Guide · Chemistry

What is the Valency of Iodine?

Iodine (Symbol: I, Atomic Number: 53) is a dark, shiny, non-metallic element. It belongs to Group 17 of the periodic table, famously known as the Halogens (along with Fluorine, Chlorine, and Bromine).

Question (Click to Flip)

Is Iodine a solid, liquid, or gas at room temperature?

Answer

Unlike Chlorine (gas) and Bromine (liquid), Iodine is a solid at room temperature. It forms dark purple/black crystals.

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Key Facts

Iodine is vital for human health! Your thyroid gland needs iodine to produce hormones. A deficiency of iodine in the diet causes a disease called Goiter, which is why salt companies sell 'Iodized Salt'.

The Primary Valency

The primary and most common valency of Iodine is 1.

Why is its valency 1? (Electronic Configuration)

The concept of valency depends entirely on the outermost shell (valence shell) of an atom.

  • The outermost shell of Iodine has exactly 7 valence electrons (s² p⁵ configuration).
  • According to the Octet Rule, every atom wants to have 8 electrons in its outer shell to become stable like a noble gas.
  • Since Iodine already has 7, it only needs to gain or share 1 more electron to reach 8. Therefore, its combining capacity (valency) is 1.

Examples in Compounds

Because its valency is 1, it usually forms simple compounds by gaining one electron to form an Iodide ion (I⁻), or by sharing one electron.

  • Potassium Iodide (KI): Potassium gives 1 electron, Iodine takes 1.
  • Hydrogen Iodide (HI): Hydrogen and Iodine share 1 electron each.

Advanced Concept: Variable Valency

While its primary valency is 1, Iodine is a large atom located lower down in the periodic table. It has empty 'd-orbitals' available. Because of this, it can 'expand its octet' and share more electrons when it reacts with highly electronegative elements (like Oxygen or Fluorine). Therefore, Iodine can also show variable valencies of 3, 5, and 7 in specific advanced compounds (e.g., IF₇ - Iodine Heptafluoride, where its valency is 7).

Questions and Answers

Is Iodine a solid, liquid, or gas at room temperature?+

Unlike Chlorine (gas) and Bromine (liquid), Iodine is a **solid** at room temperature. It forms dark purple/black crystals.

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