Question

The high reactivity of fluorine among the halogens is mainly due to:

• A. Its high electronegativity
• B. Small size of the F atom
• C. Availability of d-orbitals
• D. Strong F-F bond

Hint:

Fluorine tops the periodic table in one particular property that drives its bonding behaviour.

Answer 1

The Correct Option is A

Step 1: Fluorine is the most electronegative element in the periodic table, with an electronegativity value of about 4.0 on the Pauling scale, higher than any other element.

Step 2: Because of this very high electronegativity, fluorine pulls electron density towards itself extremely strongly in any bond it forms, which makes it eager to gain an electron and form a stable F- ion or a strongly polarised covalent bond. This strong pull towards forming bonds is the main reason fluorine reacts so readily with almost every other element.

Step 3: The small size, option B, is real and does contribute to some unusual properties of fluorine, such as its low bond dissociation energy caused by lone pair repulsion, but the primary reason usually quoted for its high reactivity is its high electronegativity, so option A is preferred over option B.

Step 4: Option C is wrong because fluorine, being in period 2, has no d-orbitals available at all, so this cannot explain anything about it. Option D is wrong because the F-F bond is actually weaker than expected, not stronger, due to repulsion between the closely packed lone pairs on the two small fluorine atoms, and this weak bond actually helps fluorine react faster, not slower.

Step 5: So the correct answer is option A, its high electronegativity.