In the molecule FCl, the atom that acts as the negative pole is fluorine (F).
Here’s why: Fluorine is more electronegative than chlorine (Cl), meaning it has a stronger ability to attract electrons towards itself. Electronegativity is a measure of how strongly an atom attracts bonding electrons, and fluorine ranks at the top of the electronegativity scale. As a result, in the FCl molecule, the shared electrons in the bond are pulled closer to the fluorine atom, creating a partial negative charge on fluorine and a partial positive charge on chlorine.
So, when we look at the F-Cl bond, we can clearly see that fluorine is the negative pole due to its higher electronegativity.