Here's why:

* Diatomic molecules are molecules composed of two atoms of the same element.

* F (Fluorine), I (Iodine), and H (Hydrogen) all exist as diatomic molecules: F₂ (Fluorine gas), I₂ (Iodine gas), and H₂ (Hydrogen gas).

* Ne (Neon) is a noble gas. Noble gases are extremely unreactive and exist as single atoms, not diatomic molecules.