The ability of an atom to attract the shared pair of electrons towards itself in a molecule is called electronegativity.
Its S.I is the Pauling-unit.
As you move from left to right across a period in the periodic table, the nuclear charge increases while the number of shielding electrons remains the same. This results in a general trend of increasing electronegativity across a period, meaning that atoms on the right side of the periodic table are more electronegative than those on the left side.
As you move down a group in the periodic table, the distance between the nucleus and the valence electrons increases, which reduces the attraction between the nucleus and the electrons. This results in a general trend of decreasing electronegativity down a group, meaning that atoms at the bottom of a group are less electronegative than those at the top.
