Final answer:
Fluorine (F) has the greatest electronegativity according to the periodic table, with a value of 3.98 on the Pauling scale.
Step-by-step explanation:
According to the trends of the periodic table, the element with the greatest electronegativity among the options provided (Li, F, Cs, At) is fluorine (F).
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. In the periodic table, electronegativity increases across a period (from left to right) and decreases down a group (from top to bottom). Hence, the element fluorine, which is located in the upper right corner of the periodic table, excluding the noble gases, has the highest electronegativity. For instance, according to Pauling's scale, fluorine has an electronegativity value of 3.98, which is the highest among all elements.