What is the Formula Mass of the Iodine Molecule?

Answer: The formula mass of the iodine molecule (I₂) is 253.8 amu.

The formula mass of a molecule refers to the sum of the atomic masses of all the atoms present in the molecular formula. In the case of iodine (I₂), it is a diatomic molecule, meaning it consists of two iodine atoms.

Atomic Mass of Iodine

The atomic mass of one iodine (I) atom is 126.9 atomic mass units (amu). Since the iodine molecule (I₂) contains two iodine atoms, its formula mass is calculated as follows:

Formula Mass of I₂=2×Atomic Mass of I\text{Formula Mass of I₂} = 2 \times \text{Atomic Mass of I} =2×126.9 amu= 2 \times 126.9 \, \text{amu} =253.8 amu= 253.8 \, \text{amu}

Thus, the formula mass of iodine (I₂) is 253.8 amu.

Explanation of Formula Mass

The formula mass is useful in chemistry for various calculations, including:

• Determining the molar mass (in grams per mole).
• Calculating stoichiometric ratios in chemical reactions.
• Understanding molecular weights in different chemical processes.

Comparison with Other Halogens

For reference, the formula masses of other halogen molecules are:

• Fluorine (F₂) → 2 × 18.99 = 37.98 amu
• Chlorine (Cl₂) → 2 × 35.45 = 70.90 amu
• Bromine (Br₂) → 2 × 79.90 = 159.80 amu
• Iodine (I₂) → 2 × 126.9 = 253.8 amu

As we move down the group in the periodic table, the atomic mass increases, leading to a higher formula mass for heavier halogens like iodine.

Applications of Iodine (I₂)

• Used as an antiseptic in medical treatments (tincture of iodine).
• Plays a role in thyroid hormone production in the human body.
• Used in chemical synthesis and disinfectants.
• Employed in starch tests, where it reacts to form a blue-black complex.

The formula mass of the iodine molecule (I₂) is 253.8 amu, derived from the atomic mass of iodine. This value is important in chemical calculations and understanding iodine’s properties in various applications.