The bond in the HF molecule is a covalent bond. However, the pair of electrons is not shared equally between the two atoms, because the fluorine atom attracts the shared electron density more strongly than does hydrogen. The tendency of an atom to attract bonding electron density is called electronegativity. Fluorine is more electronegative than hydrogen. one notes that the electronegativity of the atoms of the main group elements increases as one moves from left to right and from the bottom to the top of the periodic table.