The property of chlorine which causes hydrogen chloride to be more ionic than the chlorine molecules is its

The property of chlorine that causes hydrogen chloride to be more ionic than the chlorine molecule is its electronegativity. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. Chlorine is more electronegative than hydrogen, so in a molecule of hydrogen chloride, chlorine pulls the shared pair of electrons in the bond closer to itself, creating a partial negative charge on the chlorine atom and a partial positive charge on the hydrogen atom. This unequal sharing of electrons in the bond creates an ionic character in the molecule, making hydrogen chloride more ionic than the chlorine molecule.